⚡ validate only newly read bytes of binary-format strings

get_string() validated the whole result after each call, but get_bytes() appends to it and CBOR indefinite-length strings collect all chunks in the same result, so every chunk re-validated everything read before it. An input of many small chunks took quadratic time (80000 one-byte chunks, 160 KB of input, took about 7 seconds). Only the newly read bytes are validated now, which also matches RFC 8949's requirement that every chunk is valid UTF-8 on its own. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
🐛 reject ill-formed UTF-8 in CBOR/MessagePack/BSON text strings at decode time (#5531 )
2026-09-25 17:30:32 +00:00 · 2026-09-23 20:42:27 +02:00 · 2026-09-23 20:42:25 +02:00 · 2026-09-14 21:22:01 +02:00 · 2026-09-14 21:22:00 +02:00
154 changed files with 1611 additions and 13424 deletions
@@ -158,15 +158,6 @@ make amalgamate
 Running `make amalgamate` will also apply automatic formatting to the source files using
 [`Artistic Style`](https://astyle.sourceforge.net/). This formatting may modify your source files in-place. Be certain to review and commit any changes to avoid unintended formatting diffs in commits.

-If you add, rename, or remove a header in `include/nlohmann`, also regenerate the header list in
-[`BUILD.bazel`](https://github.com/nlohmann/json/blob/develop/BUILD.bazel) (requires CMake) by executing:
-
-```shell
-make BUILD.bazel
-```
-
-The amalgamation check in CI fails if any of these generated files is out of date.
-
 ## Recommended documentation

 - The library’s [README file](https://github.com/nlohmann/json/blob/master/README.md) is an excellent starting point to
@@ -2,7 +2,6 @@

 - [ ] The changes are described in detail, both the what and why.
 - [ ] If applicable, an [existing issue](https://github.com/nlohmann/json/issues) is referenced.
- [ ] If applicable, a fixed [OSS-Fuzz](https://issues.oss-fuzz.com) issue is referenced as `OSS-Fuzz: <id>` (see [fuzz testing](https://github.com/nlohmann/json/blob/develop/tests/fuzzing.md#handling-oss-fuzz-reports)).
 - [ ] The [Code coverage](https://coveralls.io/github/nlohmann/json) remained at 100%. A test case for every new line of code.
 - [ ] If applicable, the [documentation](https://json.nlohmann.me) is updated.
 - [ ] The source code is amalgamated by running `make amalgamate`.
@@ -29,27 +29,6 @@ labels:
  files:
    - ".github/external_ci/.*"

- label: "CI"
-  files:
-    - ".github/(dependabot|labeler)\\.yml"
-
- label: "aspect: binary formats"
-  files:
-    - "include/nlohmann/detail/input/binary_reader\\.hpp"
-    - "include/nlohmann/detail/output/binary_writer\\.hpp"
-    - "tests/src/unit-(bson|cbor|msgpack|ubjson|bjdata|binary_formats)"
-    - "tests/src/fuzzer-parse_(bson|cbor|msgpack|ubjson|bjdata)"
-    - "docs/mkdocs/docs/features/binary_formats/"
-    - "docs/mkdocs/docs/(api/basic_json|examples)/(to|from)_(bson|cbor|msgpack|ubjson|bjdata)"
-
- label: "aspect: binary formats"
-  title: "(?i)(bson|cbor|msgpack|messagepack|ubjson|bjdata|binary format)"
-
- label: "python"
-  files:
-    - "\\.py$"
-    - "requirements[^/]*\\.txt$"
-
 - label: "S"
  size-below: 10
 - label: "M"
@@ -57,16 +57,13 @@ jobs:
          python3 -mvenv venv
          venv/bin/pip3 install -r $MAIN_DIR/tools/astyle/requirements.txt

-      - name: Regenerate amalgamation, formatting, and BUILD.bazel
+      - name: Regenerate amalgamation and formatting
        run: |
          cd $MAIN_DIR

          python3 $TOOL_DIR/amalgamate.py -c $TOOL_DIR/config_json.json -s .
          python3 $TOOL_DIR/amalgamate.py -c $TOOL_DIR/config_json_fwd.json -s .

-          # the header list of the Bazel "json" target must match the files in include/
-          cmake -P cmake/scripts/gen_bazel_build_file.cmake
-
          ${{ github.workspace }}/venv/bin/astyle --project=tools/astyle/.astylerc --suffix=none --quiet \
            $INCLUDE_DIR/json.hpp $INCLUDE_DIR/json_fwd.hpp

@@ -90,7 +87,7 @@ jobs:
          mkdir -p ${{ github.workspace }}/patch
          git diff --patch --no-color > ${{ github.workspace }}/patch/amalgamation.patch
          if [ -s ${{ github.workspace }}/patch/amalgamation.patch ]; then
-            echo "The source code has not been amalgamated/formatted correctly or BUILD.bazel is out of date. Diff:"
+            echo "The source code has not been amalgamated/formatted correctly. Diff:"
            cat ${{ github.workspace }}/patch/amalgamation.patch
            echo "has_diff=true" >> "$GITHUB_OUTPUT"
          else
@@ -38,14 +38,14 @@ jobs:

    # Initializes the CodeQL tools for scanning.
    - name: Initialize CodeQL
-      uses: github/codeql-action/init@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+      uses: github/codeql-action/init@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
      with:
        languages: c-cpp

    # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
    # If this step fails, then you should remove it and run the build manually (see below)
    - name: Autobuild
-      uses: github/codeql-action/autobuild@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+      uses: github/codeql-action/autobuild@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9

    - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+      uses: github/codeql-action/analyze@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
@@ -95,13 +95,13 @@ jobs:
              issue_number: issue_number,
              owner: context.repo.owner,
              repo: context.repo.repo,
-              body: '## 🔴 Amalgamation check failed! 🔴\nThe source code has not been amalgamated and/or formatted correctly, or `BUILD.bazel` is out of date.'
+              body: '## 🔴 Amalgamation check failed! 🔴\nThe source code has not been amalgamated and/or formatted correctly.'
                    + (hasPatch ? '\n\n📎 A ready-to-apply patch is attached to the [failed workflow run](' + runUrl + ') as the `amalgamation-patch` artifact.'
                                  + ' Download it, then apply it locally from the repository root with:'
                                  + '\n\n```shell\ngit apply amalgamation.patch\n```\n\n'
                                  + 'This does not require installing astyle yourself.'
                                : '')
                    + (first ? '\n\n@' + author + ' Please read and follow the [Contribution Guidelines]'
-                               + '(https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#amalgamate-the-source-code).'
+                               + '(https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#files-to-change).'
                             : '')
              })
@@ -43,6 +43,6 @@ jobs:
          output: 'flawfinder_results.sarif'

      - name: Upload analysis results to GitHub Security tab
-        uses: github/codeql-action/upload-sarif@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+        uses: github/codeql-action/upload-sarif@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
        with:
          sarif_file: ${{github.workspace}}/flawfinder_results.sarif
@@ -76,6 +76,6 @@ jobs:

      # Upload the results to GitHub's code scanning dashboard.
      - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+        uses: github/codeql-action/upload-sarif@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
        with:
          sarif_file: results.sarif
@@ -61,7 +61,7 @@ jobs:

      # Upload SARIF file generated in previous step
      - name: Upload SARIF file
-        uses: github/codeql-action/upload-sarif@b96794f015dfd88f77b49b1c93e0fa7110f94c63 # v4.38.0
+        uses: github/codeql-action/upload-sarif@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
        with:
          sarif_file: semgrep.sarif
        if: always()
@@ -100,7 +100,7 @@ jobs:
    container: ubuntu:focal
    strategy:
      matrix:
-        target: [ci_cmake_flags, ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_noglobaludls, ci_test_disableenumserialization, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_no_thread_local]
+        target: [ci_cmake_flags, ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_noglobaludls, ci_test_simdutf]
    steps:
      - name: Install build-essential
        run: apt-get update ; apt-get install -y build-essential unzip wget git libssl-dev
@@ -124,11 +124,11 @@ jobs:
    steps:
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
      - name: Run CMake (Release)
-        run: cmake -S . -B build -G "Visual Studio 18 2026" -A ARM64 -DJSON_BuildTests=On -DCMAKE_CXX_FLAGS="/W4 /WX"
+        run: cmake -S . -B build -G "Visual Studio 17 2022" -A ARM64 -DJSON_BuildTests=On -DCMAKE_CXX_FLAGS="/W4 /WX"
        if: matrix.build_type == 'Release'
        shell: pwsh
      - name: Run CMake (Debug)
-        run: cmake -S . -B build -G "Visual Studio 18 2026" -A ARM64 -DJSON_BuildTests=On -DJSON_FastTests=ON -DCMAKE_CXX_FLAGS="/W4 /WX"
+        run: cmake -S . -B build -G "Visual Studio 17 2022" -A ARM64 -DJSON_BuildTests=On -DJSON_FastTests=ON -DCMAKE_CXX_FLAGS="/W4 /WX"
        if: matrix.build_type == 'Debug'
        shell: pwsh
      - name: Build
@@ -158,10 +158,6 @@ jobs:
      # to fit: IMAGE_REL_AMD64_SECREL against `.debug_line'" because the
      # MinGW linker cannot relocate the debug sections this test produces.
      # The tests are only built and run here, so the debug info is not used.
-      # Do not add -O1 here to shrink the objects further: it does make them
-      # link, but the binaries clang 11.0.1 and clang 18.1.8 then produce crash
-      # before doctest prints its first line - 39 of 102 tests on clang 18.
-      # Keep the objects small by splitting the test files instead.
      - name: Run CMake
        run: cmake -S . -B build ^
             -DCMAKE_CXX_COMPILER="C:/Program Files/LLVM/bin/clang++.exe" ^
@@ -30,10 +30,8 @@ cc_library(
        "include/nlohmann/detail/input/input_adapters.hpp",
        "include/nlohmann/detail/input/json_sax.hpp",
        "include/nlohmann/detail/input/lexer.hpp",
-        "include/nlohmann/detail/input/number_parse.hpp",
        "include/nlohmann/detail/input/parser.hpp",
        "include/nlohmann/detail/input/position_t.hpp",
-        "include/nlohmann/detail/input/string_scan.hpp",
        "include/nlohmann/detail/iterators/internal_iterator.hpp",
        "include/nlohmann/detail/iterators/iter_impl.hpp",
        "include/nlohmann/detail/iterators/iteration_proxy.hpp",
@@ -51,14 +49,12 @@ cc_library(
        "include/nlohmann/detail/meta/detected.hpp",
        "include/nlohmann/detail/meta/identity_tag.hpp",
        "include/nlohmann/detail/meta/is_sax.hpp",
-        "include/nlohmann/detail/meta/logic.hpp",
        "include/nlohmann/detail/meta/std_fs.hpp",
        "include/nlohmann/detail/meta/type_traits.hpp",
        "include/nlohmann/detail/meta/void_t.hpp",
        "include/nlohmann/detail/output/binary_writer.hpp",
        "include/nlohmann/detail/output/output_adapters.hpp",
        "include/nlohmann/detail/output/serializer.hpp",
-        "include/nlohmann/detail/recursion_depth_limit.hpp",
        "include/nlohmann/detail/string_concat.hpp",
        "include/nlohmann/detail/string_escape.hpp",
        "include/nlohmann/detail/string_utils.hpp",
@@ -71,6 +67,7 @@ cc_library(
    ],
    includes = ["include"],
    visibility = ["//visibility:public"],
+    alwayslink = True,
 )

 cc_library(
@@ -59,7 +59,6 @@ option(JSON_LegacyDiscardedValueComparison "Enable legacy discarded value compar
 option(JSON_Install                        "Install CMake targets during install step." ${MAIN_PROJECT})
 option(JSON_MultipleHeaders                "Use non-amalgamated version of the library." ON)
 option(JSON_SystemInclude                  "Include as system headers (skip for clang-tidy)." OFF)
-option(JSON_StrictNulHandling              "Build with strict NUL-byte handling enabled." OFF)

 if (JSON_CI)
    include(ci)
@@ -109,10 +108,6 @@ if (JSON_Diagnostics)
    message(STATUS "Diagnostics enabled (JSON_DIAGNOSTICS=1)")
 endif()

-if (JSON_StrictNulHandling)
-    message(STATUS "Strict NUL-byte handling enabled (JSON_STRICT_NUL_HANDLING=1)")
-endif()
-
 if (JSON_Diagnostic_Positions)
    message(STATUS "Diagnostic positions enabled (JSON_DIAGNOSTIC_POSITIONS=1)")
 endif()
@@ -146,7 +141,6 @@ target_compile_definitions(
    $<$<BOOL:${JSON_Diagnostics}>:JSON_DIAGNOSTICS=1>
    $<$<BOOL:${JSON_Diagnostic_Positions}>:JSON_DIAGNOSTIC_POSITIONS=1>
    $<$<BOOL:${JSON_LegacyDiscardedValueComparison}>:JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON=1>
-    $<$<BOOL:${JSON_StrictNulHandling}>:JSON_STRICT_NUL_HANDLING=1>
 )

 target_include_directories(
@@ -250,16 +250,12 @@ Further documentation:

 ### `BUILD.bazel`

-The build definition for [Bazel](https://bazel.build). The file is generated by
-`cmake/scripts/gen_bazel_build_file.cmake`, which derives the header list from the files in `include`; change the
-script rather than editing the file by hand. The file can be updated by calling
+The file can be updated by calling

 ```shell
 make BUILD.bazel
 ```

-The "Check amalgamation" workflow fails if the file is out of date.
-
 ### `meson.build`

 The build definition for the [Meson](https://mesonbuild.com) build system.
@@ -1,4 +1,4 @@
-.PHONY: pretty clean ChangeLog.md release update_hedley update_hedley_undef BUILD.bazel
+.PHONY: pretty clean ChangeLog.md release update_hedley update_hedley_undef

 ##########################################################################
 # configuration
@@ -30,9 +30,8 @@ AMALGAMATED_FWD_FILE=single_include/nlohmann/json_fwd.hpp
 # main target
 all:
 	@echo "amalgamate - amalgamate files single_include/nlohmann/json{,_fwd}.hpp from the include/nlohmann sources"
-	@echo "BUILD.bazel - regenerate the Bazel BUILD file from the include/nlohmann sources"
 	@echo "ChangeLog.md - generate ChangeLog file"
-	@echo "check-amalgamation - check whether sources have been amalgamated and BUILD.bazel is up to date"
+	@echo "check-amalgamation - check whether sources have been amalgamated"
 	@echo "clean - remove built files"
 	@echo "doctest - compile example files and check their output"
 	@echo "fuzz_testing - prepare fuzz testing of the JSON parser"
@@ -173,13 +172,8 @@ check-amalgamation:
 	@diff $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_FWD_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE) ; false)
 	@mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE)
 	@mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE)
-	@mv BUILD.bazel BUILD.bazel~
-	@$(MAKE) BUILD.bazel
-	@diff BUILD.bazel BUILD.bazel~ || (echo "===================================================================\n  BUILD.bazel is out of date! Please run 'make BUILD.bazel'.\n===================================================================" ; mv BUILD.bazel~ BUILD.bazel ; false)
-	@mv BUILD.bazel~ BUILD.bazel

-# generate the Bazel BUILD file; phony, because a removed header would not trigger a rebuild
-BUILD.bazel:
+BUILD.bazel: $(SRCS)
 	cmake -P cmake/scripts/gen_bazel_build_file.cmake

 ##########################################################################
@@ -1421,7 +1421,7 @@ I deeply appreciate the help of the following people.
 6. [Joshua C. Randall](https://github.com/jrandall) fixed a bug in the floating-point serialization.
 7. [Aaron Burghardt](https://github.com/aburgh) implemented code to parse streams incrementally. Furthermore, he greatly improved the parser class by allowing the definition of a filter function to discard undesired elements while parsing.
 8. [Daniel Kopeček](https://github.com/dkopecek) fixed a bug in the compilation with GCC 5.0.
-9. [Fiona Johanna Weber](https://github.com/Fiona-J-W) fixed a bug in and improved the performance of the comparison operators.
+9. [Florian Weber](https://github.com/Florianjw) fixed a bug in and improved the performance of the comparison operators.
 10. [Eric Cornelius](https://github.com/EricMCornelius) pointed out a bug in the handling with NaN and infinity values. He also improved the performance of the string escaping.
 11. [易思龙](https://github.com/likebeta) implemented a conversion from anonymous enums.
 12. [kepkin](https://github.com/kepkin) patiently pushed forward the support for Microsoft Visual Studio.
@@ -1523,14 +1523,14 @@ I deeply appreciate the help of the following people.
 108. [Kevin Tonon](https://github.com/ktonon) overworked the C++11 compiler checks in CMake.
 109. [Axel Huebl](https://github.com/ax3l) simplified a CMake check and added support for the [Spack package manager](https://spack.io).
 110. [Carlos O'Ryan](https://github.com/coryan) fixed a typo.
-111. [James Upjohn](https://github.com/jupjohn) fixed a version number in the compilers section.
+111. [James Upjohn](https://github.com/jammehcow) fixed a version number in the compilers section.
 112. [Chuck Atkins](https://github.com/chuckatkins) adjusted the CMake files to the CMake packaging guidelines and provided documentation for the CMake integration.
 113. [Jan Schöppach](https://github.com/dns13) fixed a typo.
 114. [martin-mfg](https://github.com/martin-mfg) fixed a typo.
 115. [Matthias Möller](https://github.com/TinyTinni) removed the dependency from `std::stringstream`.
 116. [agrianius](https://github.com/agrianius) added code to use alternative string implementations.
 117. [Daniel599](https://github.com/Daniel599) allowed to use more algorithms with the `items()` function.
-118. [Julius Rakow](https://github.com/juliusrakow) fixed the Meson include directory and fixed the links to [cppreference.com](https://cppreference.com).
+118. [Julius Rakow](https://github.com/jrakow) fixed the Meson include directory and fixed the links to [cppreference.com](https://cppreference.com).
 119. [Sonu Lohani](https://github.com/sonulohani) fixed the compilation with MSVC 2015 in debug mode.
 120. [grembo](https://github.com/grembo) fixed the test suite and re-enabled several test cases.
 121. [Hyeon Kim](https://github.com/simnalamburt) introduced the macro `JSON_INTERNAL_CATCH` to control the exception handling inside the library.
@@ -1581,7 +1581,7 @@ I deeply appreciate the help of the following people.
 166. [Mark Beckwith](https://github.com/wythe) fixed a typo.
 167. [yann-morin-1998](https://github.com/yann-morin-1998) helped to reduce the CMake requirement to version 3.1.
 168. [Konstantin Podsvirov](https://github.com/podsvirov) maintains a package for the MSYS2 software distro.
-169. [remyabel](https://github.com/remyabel2) added GNUInstallDirs to the CMake files.
+169. [remyabel](https://github.com/remyabel) added GNUInstallDirs to the CMake files.
 170. [Taylor Howard](https://github.com/taylorhoward92) fixed a unit test.
 171. [Gabe Ron](https://github.com/Macr0Nerd) implemented the `to_string` method.
 172. [Watal M. Iwasaki](https://github.com/heavywatal) fixed a Clang warning.
@@ -1608,7 +1608,7 @@ I deeply appreciate the help of the following people.
 193. [Hubert Chathi](https://github.com/uhoreg) made CMake's version config file architecture-independent.
 194. [OmnipotentEntity](https://github.com/OmnipotentEntity) implemented the binary values for CBOR, MessagePack, BSON, and UBJSON.
 195. [ArtemSarmini](https://github.com/ArtemSarmini) fixed a compilation issue with GCC 10 and fixed a leak.
-196. [Evgenii Sopov](https://github.com/sea5kg) integrated the library to the wsjcpp package manager.
+196. [Evgenii Sopov](https://github.com/sea-kg) integrated the library to the wsjcpp package manager.
 197. [Sergey Linev](https://github.com/linev) fixed a compiler warning.
 198. [Miguel Magalhães](https://github.com/magamig) fixed the year in the copyright.
 199. [Gareth Sylvester-Bradley](https://github.com/garethsb-sony) fixed a compilation issue with MSVC.
@@ -1702,7 +1702,7 @@ I deeply appreciate the help of the following people.
 287. [NN](https://github.com/NN---) added the Visual Studio output directory to `.gitignore`.
 288. [Romain Reignier](https://github.com/romainreignier) improved the performance of the vector output adapter.
 289. [Mike](https://github.com/Mike-Leo-Smith) fixed the `std::iterator_traits`.
-290. [Richard Hozák](https://github.com/richardhozak) added macro `JSON_NO_ENUM` to disable default enum conversions.
+290. [Richard Hozák](https://github.com/zxey) added macro `JSON_NO_ENUM` to disable default enum conversions.
 291. [vakokako](https://github.com/vakokako) fixed tests when compiling with C++20.
 292. [Alexander “weej” Jones](https://github.com/alexweej) fixed an example in the README.
 293. [Eli Schwartz](https://github.com/eli-schwartz) added more files to the `include.zip` archive.
@@ -1727,7 +1727,7 @@ I deeply appreciate the help of the following people.
 312. [Gareth Sylvester-Bradley](https://github.com/garethsb) added `operator/=` and `operator/` to construct JSON pointers.
 313. [Michael Macnair](https://github.com/mykter) added support for afl-fuzz testing.
 314. [Berkus Decker](https://github.com/berkus) fixed a typo in the README.
-315. [Illia Polishchuk](https://github.com/ilqvya) improved the CMake testing.
+315. [Illia Polishchuk](https://github.com/effolkronium) improved the CMake testing.
 316. [Ikko Ashimine](https://github.com/eltociear) fixed a typo.
 317. [Raphael Grimm](https://github.com/barcode) added the possibility to define a custom base class.
 318. [tocic](https://github.com/tocic) fixed typos in the documentation.
@@ -1797,66 +1797,6 @@ I deeply appreciate the help of the following people.
 382. [bitFiedler](https://github.com/bitFiedler) made GDB pretty printer work with Python 3.8.
 383. [Gianfranco Costamagna](https://github.com/LocutusOfBorg) fixed a compiler warning.
 384. [risa2000](https://github.com/risa2000) made `std::filesystem::path` conversion to/from UTF-8 encoded string explicit.
-385. [AM](https://github.com/maqnouch) fixed typos in the README.
-386. [dmenendez-gruposantander](https://github.com/dmenendez-gruposantander) fixed typos in the comments of the examples.
-387. [Mihai Stan](https://github.com/mstan-xx) fixed comparisons against the literal `0`.
-388. [Matt Gumbel](https://github.com/intelmatt) fixed some `-Weffc++` warnings.
-389. [vimpunk](https://github.com/vimpunk) moved a lambda out of an unevaluated context to support older compilers.
-390. [Chris Harris](https://github.com/cjh1) fixed the compilation with GCC 4.8.
-391. [Palmer Dabbelt](https://github.com/palmer-dabbelt) generated and installed a pkg-config file.
-392. [Gus Pozuelo](https://github.com/ap-viavi) made `ordered_map` compatible with GCC 5.5, Clang 3.6, and Xcode 9.
-393. [AK](https://github.com/Lioncky) fixed an MSVC build error caused by the `min`/`max` macros from `windows.h`.
-394. [Sergiu Deitsch](https://github.com/sergiud) provided a fallback for missing `char8_t` support.
-395. [Xiaochuan Ye](https://github.com/XueSongTap) fixed `from_msgpack` for `std::byte` input by specializing `std::char_traits`.
-396. [Ville Vesilehto](https://github.com/thevilledev) fixed an overflow in the BJData size calculation and rejected overflowing negative integers in CBOR.
-397. [NmPassTHFan](https://github.com/nmpassthf) replaced the deprecated `std::is_trivial` for C++26.
-398. [Chris Ever](https://github.com/chirsz-ever) added the `ignore_trailing_commas` parser option.
-399. [Kuan-Fu Wu](https://github.com/kfwu1999) fixed the example code for `json_pointer` initialization.
-400. [David Kilzer](https://github.com/ddkilzer) added a missing header to the input adapters.
-401. [Miko](https://github.com/mikomikotaishi) added proper C++20 module support, simplified the module API, and fixed missing exports.
-402. [hitgirl](https://github.com/hitgil) fixed the CMake configuration when cross-compiling.
-403. [Devon Thomas](https://github.com/ThomaDevOSU) mentioned the Artistic Style formatting in the contribution guidelines.
-404. [Erik Hu](https://github.com/Erikhu1) made Coveralls upload errors non-fatal in the CI.
-405. [co63oc](https://github.com/co63oc) fixed typos.
-406. [DmitriBogdanov](https://github.com/DmitriBogdanov) fixed broken package manager links in the documentation.
-407. [Bander](https://github.com/banderzhm) improved the MSVC compatibility of the C++ modules.
-408. [Andy Choi](https://github.com/ccpong) removed an unnecessary `template` keyword before `get` in the README and the documentation.
-409. [SamareshSingh](https://github.com/ssam18) fixed single-element brace initialization to copy/move instead of wrapping in an array, fixed the `WITH_DEFAULT` macros for `ordered_map`, and handled moved events in `serve_header.py`.
-410. [Aditya](https://github.com/Lumowhisp) improved the documentation of the documentation generation.
-411. [cheese1](https://github.com/cheese1) clarified the README.
-412. [KhloodElhossiny](https://github.com/khloodelhossiny) enabled `std::string_view` keys in `operator[]`.
-413. [Charles Cabergs](https://github.com/cacharle) fixed a `-Wtautological-constant-out-of-range-compare` warning.
-414. [EALePain](https://github.com/EALePain) made the `std::tuple` conversion work with reference types such as `std::tie`.
-415. [koala_oishi](https://github.com/chibi-dogs) fixed grammatical wording in the README.
-416. [riccardoori11](https://github.com/riccardoori11) fixed a typo in the documentation.
-417. [Swastik Bose](https://github.com/VasuBhakt) fixed the parent pointers after `update()` with `JSON_DIAGNOSTICS` and fixed the Doxygen autolinking of requirements.
-418. [trdesilva](https://github.com/trdesilva) added `front`, `pop_front`, and `push_front` to `json_pointer`.
-419. [Akhilesh Arora](https://github.com/akhilesharora) fixed an incomplete-type error with `ordered_json`.
-420. [Hariom Phulre](https://github.com/hariomphulre) fixed the C++20 modules compilation with GCC.
-421. [Kirill Lokotkov](https://github.com/RUSLoker) fixed printing `long double` values.
-422. [George Sedov](https://github.com/radistmorse) added the `NLOHMANN_DEFINE_TYPE_*_WITH_NAMES` macros.
-423. [Caillin Nugent](https://github.com/nugentcaillin) added the `NLOHMANN_JSON_SERIALIZE_ENUM_STRICT` macro.
-424. [Cosmin D.](https://github.com/drcosmin) fixed `std::filesystem::path` conversions and added an MSVC workaround for `std::unique_ptr`.
-425. [Paul Dreik](https://github.com/pauldreik) fixed a test relying on implementation-specific behavior.
-426. [Daniel Falk](https://github.com/daniel-falk) added missing copyright notices to the SBOM.
-427. [Federico Sfriso](https://github.com/federicosfriso05-dotcom) added support for constructing JSON values from C++20 range views.
-428. [Luke Banicevic](https://github.com/banaboi) fixed corrupt BSON output for lengths exceeding `INT32_MAX`, cleaned up the BSON writer, and improved the documentation.
-429. [Patrick Armstrong](https://github.com/Patrick10199) updated the CBOR references and the half-precision float assertions.
-430. [Yash Bavadiya](https://github.com/xevrion) added checks to all BSON reads.
-431. [hum4nBeing](https://github.com/hum4nBeing) fixed the overflow handling of high-precision numbers in UBJSON.
-432. [tomatotomata](https://github.com/tomatotomata) added checks for reading CBOR tagged subtypes.
-433. [YingqiDuan](https://github.com/YingqiDuan) documented the BSON interoperability.
-434. [KBS](https://github.com/youdie006) documented the standards compliance and the strictness of `parse()` and `operator>>`.
-435. [Petr Bělohlávek](https://github.com/petrbel) added Clang 21 and 22 to the CI.
-436. [Dmitry Rantovov](https://github.com/darkdi) fixed the placement of a CBOR documentation block.
-437. [ljcjclljc](https://github.com/ljcjclljc) fixed the comparison of large unsigned integers with signed integers.
-438. [Sahil Kamate](https://github.com/sahilkamate03) fixed the handling of CBOR tags 0-5 and 21-23.
-439. [Krishnanand G](https://github.com/Krishnanand-G) made the UBJSON writer reject `use_type` without `use_size`.
-440. [whn](https://github.com/Whning0513) documented the lenient BSON input handling and corrected the complexity of `to_bson`.
-441. [elix3r](https://github.com/22elix3r) fixed `update()` with `merge_objects` when merging a primitive into an object.
-442. [Avionic Harshit](https://github.com/avionicharshit-byte) made `diff()` linear when an array shrinks.
-443. [Qatadaha Bin Matloob](https://github.com/qatcod) fixed comparisons between integers and floats and fixed unparsable BJData output.
-444. [Wu Shuwen](https://github.com/dajiaohuang) removed an unused include.

 Thanks a lot for helping out! Please [let me know](mailto:mail@nlohmann.me) if I forgot someone.

@@ -231,20 +231,18 @@ add_custom_target(ci_test_simdutf
 )

 ###############################################################################
-# Enable strict NUL-byte handling.
+# Enable brace-init copy semantics.
 ###############################################################################

-add_custom_target(ci_test_strict_nul_handling
+add_custom_target(ci_test_brace_init_copy_semantics
    COMMAND ${CMAKE_COMMAND}
    -DCMAKE_BUILD_TYPE=Debug -GNinja
-    -DJSON_BuildTests=ON -DJSON_FastTests=ON -DJSON_StrictNulHandling=ON
-    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_strict_nul_handling
-    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_strict_nul_handling
-    # unit-testsuites contains a fixture (a "1e308" test value) that relies on the
-    # legacy NUL-as-end-of-input behavior this macro disables; exclude it here, as
-    # it is expected to fail under strict NUL handling and is out of scope for it
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_strict_nul_handling && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure -E "test-testsuites"
-    COMMENT "Compile and test with strict NUL-byte handling enabled"
+    -DJSON_BuildTests=ON -DJSON_FastTests=ON
+    -DCMAKE_CXX_FLAGS=-DJSON_BRACE_INIT_COPY_SEMANTICS=1
+    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_brace_init_copy_semantics
+    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_brace_init_copy_semantics
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_brace_init_copy_semantics && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
+    COMMENT "Compile and test with brace-init copy semantics enabled"
 )

 ###############################################################################
@@ -262,59 +260,6 @@ add_custom_target(ci_test_noglobaludls
    COMMENT "Compile and test with global UDLs disabled"
 )

-###############################################################################
-# Disable enum serialization.
-###############################################################################
-
-add_custom_target(ci_test_disableenumserialization
-    COMMAND ${CMAKE_COMMAND}
-    -DCMAKE_BUILD_TYPE=Debug -GNinja
-    -DJSON_BuildTests=ON -DJSON_FastTests=ON -DJSON_DisableEnumSerialization=ON
-    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_disableenumserialization
-    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_disableenumserialization
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_disableenumserialization && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
-    COMMENT "Compile and test with enum serialization disabled"
-)
-
-###############################################################################
-# Skip the multiple-inclusion library version check.
-###############################################################################
-
-# tests/src/skip_library_version_check.cpp deliberately simulates a scenario
-# (mixing two differently-versioned inclusions of the library in one
-# translation unit) that unavoidably triggers the compiler's own "macro
-# redefined" warning, so -- unlike the ci_test_* targets above -- it is
-# compiled directly here, with a modest warning set, instead of being folded
-# into the library's own -Weverything/-Werror unit test matrix.
-add_custom_target(ci_test_skiplibraryversioncheck
-    COMMAND ${CMAKE_COMMAND} -E make_directory ${PROJECT_BINARY_DIR}/skip_library_version_check
-    COMMAND ${CMAKE_CXX_COMPILER} -std=c++11 -Wall -Wextra
-        -I${PROJECT_SOURCE_DIR}/include
-        ${PROJECT_SOURCE_DIR}/tests/src/skip_library_version_check.cpp
-        -o ${PROJECT_BINARY_DIR}/skip_library_version_check/skip_library_version_check
-    COMMAND ${PROJECT_BINARY_DIR}/skip_library_version_check/skip_library_version_check
-    COMMENT "Compile and run a translation unit simulating a mismatched library version, with JSON_SKIP_LIBRARY_VERSION_CHECK defined"
-)
-
-###############################################################################
-# Disable thread-local storage.
-###############################################################################
-
-# Without thread-local storage, copying and comparing cannot bound their
-# descent and handle every object and array without the call stack. Those paths
-# are otherwise only reached by values nested deeper than the bound, so this
-# target is what runs the whole test suite through them.
-add_custom_target(ci_test_no_thread_local
-    COMMAND ${CMAKE_COMMAND}
-    -DCMAKE_BUILD_TYPE=Debug -GNinja
-    -DJSON_BuildTests=ON
-    -DCMAKE_CXX_FLAGS=-DJSON_NO_THREAD_LOCAL
-    -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_no_thread_local
-    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_no_thread_local
-    COMMAND cd ${PROJECT_BINARY_DIR}/build_no_thread_local && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
-    COMMENT "Compile and test without thread-local storage"
-)
-
 ###############################################################################
 # Coverage.
 ###############################################################################
@@ -1,57 +1,24 @@
 # generate Bazel BUILD file
-#
-# usage: cmake -P cmake/scripts/gen_bazel_build_file.cmake (or: make BUILD.bazel)
-#
-# The header list of the "json" target is derived from the files in include/. Everything else is fixed text below,
-# so edit this script rather than BUILD.bazel.

-get_filename_component(PROJECT_ROOT "${CMAKE_CURRENT_LIST_DIR}/../.." ABSOLUTE)
+set(PROJECT_ROOT "${CMAKE_CURRENT_LIST_DIR}/../..")
 set(BUILD_FILE "${PROJECT_ROOT}/BUILD.bazel")

-file(GLOB_RECURSE HEADERS LIST_DIRECTORIES false RELATIVE "${PROJECT_ROOT}" "${PROJECT_ROOT}/include/*.hpp")
-list(SORT HEADERS)
-
-set(CONTENT [=[
-load("@rules_cc//cc:cc_library.bzl", "cc_library")
-load("@rules_license//rules:license.bzl", "license")
-
-package(
-    default_applicable_licenses = [":license"],
-)
-
-exports_files([
-    "LICENSE.MIT",
-])
-
-license(
-    name = "license",
-    license_kinds = ["@rules_license//licenses/spdx:MIT"],
-    license_text = "LICENSE.MIT",
-)
+file(GLOB_RECURSE HEADERS LIST_DIRECTORIES false RELATIVE "${PROJECT_ROOT}" "include/*.hpp")

+file(WRITE "${BUILD_FILE}" [=[
 cc_library(
    name = "json",
    hdrs = [
 ]=])

 foreach(header ${HEADERS})
-    string(APPEND CONTENT "        \"${header}\",\n")
+    file(APPEND "${BUILD_FILE}" "        \"${header}\",\n")
 endforeach()

-string(APPEND CONTENT [=[
+file(APPEND "${BUILD_FILE}" [=[
    ],
    includes = ["include"],
    visibility = ["//visibility:public"],
-)
-
-cc_library(
-    name = "singleheader-json",
-    hdrs = [
-        "single_include/nlohmann/json.hpp",
-    ],
-    includes = ["single_include"],
-    visibility = ["//visibility:public"],
+    alwayslink = True,
 )
 ]=])
-
-file(WRITE "${BUILD_FILE}" "${CONTENT}")
@@ -90,10 +90,6 @@ Linear in the length of the input. The parser is a predictive LL(1) parser.

 A UTF-8 byte order mark is silently ignored.

-By default, a `'\0'` (NUL) byte anywhere in the input is treated as end of input, rather than as an ordinary (and,
-outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-bytes-in-the-input) for details and the
-[`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) macro to opt into rejecting it instead.
-
 ## Examples

 ??? example
@@ -115,8 +111,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
 - [parse](parse.md) - deserialize from a compatible input
 - [sax_parse](sax_parse.md) - parse input using the SAX interface
 - [operator>>](../operator_gtgt.md) - deserialize from stream
- [`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
-  instead of treating it as end of input

 ## Version history

@@ -126,8 +120,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
 - Added `ignore_trailing_commas` in version 3.13.0.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
- `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
-  it as end of input; planned to become the default in version 4.0.0.

 !!! warning "Deprecation"

@@ -14,11 +14,7 @@ To store objects in C++, a type is defined by the template parameters explained
 ## Template parameters

 `ArrayType`
-:   container type to store arrays. It must be a vector-like container: the library uses `operator[]`, `at()`, and
-    `resize()`, and requires random-access iterators. `#!cpp std::vector` and `#!cpp std::deque` qualify;
-    `#!cpp std::list` does not. See
-    [Template Parameter Requirements](../../features/types/template_parameters.md#arraytype) for the full list of
-    requirements.
+:   container type to store arrays (e.g., `std::vector` or `std::list`)

 `AllocatorType`
 :   the allocator to use for objects (e.g., `std::allocator`)
@@ -70,4 +66,3 @@ Arrays are stored as pointers in a `basic_json` type. That is, for any access to
 ## Version history

 - Added in version 1.0.0.
- Made `capacity()` optional, so that array types such as `#!cpp std::deque` can be used, in version 3.13.0.
@@ -42,9 +42,7 @@ represent a byte array in modern C++.
    `value_type` must additionally be exactly one byte wide (e.g., `std::uint8_t`/`char`/`std::byte`): the binary
    serializers (CBOR, MessagePack, BSON, UBJSON) read and write the container's raw bytes via
    `reinterpret_cast`, which is only correct for byte-sized elements -- a container like
-    `#!cpp std::vector<std::intptr_t>` will not work as `BinaryType`. The elements must be stored contiguously, and
-    the binary readers additionally require `resize()` and `operator[]`. See
-    [Template Parameter Requirements](../../features/types/template_parameters.md#binarytype) for the full list.
+    `#!cpp std::vector<std::intptr_t>` will not work as `BinaryType`.

 ## Notes

@@ -52,11 +50,6 @@ represent a byte array in modern C++.

 The default values for `BinaryType` is `#!cpp std::vector<std::uint8_t>`.

-#### Supported byte types
-
-`#!cpp std::vector<std::uint8_t>`, `#!cpp std::vector<char>`, and `#!cpp std::vector<std::byte>` are supported.
-Regardless of which of them is configured, [`dump`](dump.md) writes the bytes as the numbers 0..255.
-
 #### Custom BinaryType behavior

 When a custom `BinaryType` is configured (other than the default `#!cpp std::vector<std::uint8_t>`), you can assign
@@ -133,6 +126,3 @@ type `#!cpp binary_t*` must be dereferenced.
 ## Version history

 - Added in version 3.8.0. Changed the type of subtype to `std::uint64_t` in version 3.10.0.
- Fixed [`dump`](dump.md), [`std::hash`](std_hash.md), and [`to_ubjson`](to_ubjson.md) for byte types that are not
-  integers (e.g., `#!cpp std::byte`) in version 3.13.0. `dump` now writes the bytes of a signed byte type (e.g.,
-  `#!cpp char`) as 0..255 rather than as negative numbers.
@@ -11,14 +11,6 @@ literals `#!json true` and `#!json false`.

 To store boolean values in C++, a type is defined by the template parameter  `BooleanType` which chooses the type to use.

-## Template parameters
-
-`BooleanType`
-:   the type to store booleans. As it is stored directly inside a `basic_json` value (in a union), it must be a
-    trivially default-constructible, trivially copyable, and trivially destructible type that is convertible to and
-    from `#!cpp bool`. See
-    [Template Parameter Requirements](../../features/types/template_parameters.md#booleantype).
-
 ## Notes

 #### Default type
@@ -21,10 +21,6 @@ This overload is chosen if:
 - `ValueType` is not `basic_json`,
 - `json_serializer<ValueType>` has a `from_json()` method of the form `void from_json(const basic_json&, ValueType&)`

-`v` must not be `const`. Passing a `const` object is a compile-time error. For types such as arithmetic types, enums,
-and C arrays, the error is a `static_assert` that names the problem. For other types, the overload is not viable, and
-the compiler reports that no matching `get_to` was found.
-
 ## Template parameters

 `ValueType`
@@ -71,4 +67,3 @@ Depends on the `json_serializer<ValueType>::from_json()` implementation.
 ## Version history

 - Since version 3.3.0.
- Added a `static_assert` with a clear message for `const` arguments in version 3.13.0.
@@ -35,10 +35,6 @@ class basic_json;
 | `BinaryType`         | type for binary arrays                                                    | [`binary_t`](binary_t.md)                   |
 | `CustomBaseClass`    | extension point for user code                                             | [`json_base_class_t`](json_base_class_t.md) |

-The library imposes a number of requirements on these types that are not expressed as C++ concepts, such as the
-container operations `object_t` and `array_t` must provide, or the fact that `StringType` must be `char`-based. They
-are collected in [Template Parameter Requirements](../../features/types/template_parameters.md).
-
 ## Specializations

 - [**json**](../json.md) - default specialization
@@ -88,8 +88,6 @@ Strong exception safety: if an exception occurs, the original value stays intact
      do not belong to the same JSON value; example: `"iterators do not fit"`
    - Throws [`invalid_iterator.211`](../../home/exceptions.md#jsonexceptioninvalid_iterator211) if `first` or `last`
      are iterators into container for which insert is called; example: `"passed iterators may not belong to container"`
-    - Throws [`invalid_iterator.202`](../../home/exceptions.md#jsonexceptioninvalid_iterator202) if `first` or `last`
-      do not point to an array; example: `"iterators first and last must point to arrays"`
 4. The function can throw the following exceptions:
    - Throws [`type_error.309`](../../home/exceptions.md#jsonexceptiontype_error309) if called on JSON values other than
      arrays; example: `"cannot use insert() with string"`
@@ -21,11 +21,8 @@ The default value for `CustomBaseClass` is `void`. In this case, an

 #### Limitations

-The type `CustomBaseClass` has to be a default-constructible, non-`final` class.
+The type `CustomBaseClass` has to be a default-constructible class.
 `basic_json` only supports copy/move construction/assignment if `CustomBaseClass` does so as well.
-A `CustomBaseClass` with non-static data members forfeits `basic_json`'s
-[standard layout](https://en.cppreference.com/w/cpp/named_req/StandardLayoutType) guarantee. See
-[Template Parameter Requirements](../../features/types/template_parameters.md#custombaseclass).

 ## Examples

@@ -19,12 +19,6 @@ using json_serializer = JSONSerializer<T, SFINAE>;

 The default values for `json_serializer` is [`adl_serializer`](../adl_serializer/index.md).

-#### Requirements
-
-A custom serializer must provide `#!cpp static void to_json(basic_json&, T)` for every type it serializes, and either
-`#!cpp static void from_json(const basic_json&, T&)` or `#!cpp static T from_json(const basic_json&)` for every type it
-deserializes. See [Template Parameter Requirements](../../features/types/template_parameters.md#jsonserializer).
-
 ## Examples

 ??? example
@@ -20,16 +20,6 @@ used.
 To store floating-point numbers in C++, a type is defined by the template parameter `NumberFloatType` which chooses the
 type to use.

-## Template parameters
-
-`NumberFloatType`
-:   the type to store floating-point numbers. Parsing and serialization are implemented in terms of
-    `#!cpp std::strtof`/`#!cpp std::strtod`/`#!cpp std::strtold` and `#!cpp std::snprintf`, so the type must be
-    `#!cpp float`, `#!cpp double`, or `#!cpp long double`. The
-    [binary formats](../../features/binary_formats/index.md) additionally require `#!cpp float` or `#!cpp double`,
-    because they have no encoding for `#!cpp long double`. See
-    [Template Parameter Requirements](../../features/types/template_parameters.md#numberfloattype).
-
 ## Notes

 #### Default type
@@ -20,13 +20,6 @@ used.
 To store integer numbers in C++, a type is defined by the template parameter `NumberIntegerType` which chooses the type
 to use.

-## Template parameters
-
-`NumberIntegerType`
-:   the type to store signed integers. It must be a **signed integral** type (`#!cpp std::is_integral`) with a
-    `#!cpp std::numeric_limits` specialization, and it is stored directly inside a `basic_json` value. See
-    [Template Parameter Requirements](../../features/types/template_parameters.md#numberintegertype-and-numberunsignedtype).
-
 ## Notes

 #### Default type
@@ -20,14 +20,6 @@ used.
 To store unsigned integer numbers in C++, a type is defined by the template parameter `NumberUnsignedType` which chooses
 the type to use.

-## Template parameters
-
-`NumberUnsignedType`
-:   the type to store unsigned integers. It must be an **unsigned integral** type (`#!cpp std::is_integral`) with a
-    `#!cpp std::numeric_limits` specialization, and it must be able to represent the absolute value of every
-    [`number_integer_t`](number_integer_t.md) value. See
-    [Template Parameter Requirements](../../features/types/template_parameters.md#numberintegertype-and-numberunsignedtype).
-
 ## Notes

 #### Default type
@@ -30,5 +30,3 @@ and [`default_object_comparator_t`](default_object_comparator_t.md) otherwise.
 - Added in version 3.0.0.
 - Changed to be conditionally defined as `#!cpp typename object_t::key_compare` or `default_object_comparator_t` in
  version 3.11.0.
- Fixed the fallback to `default_object_comparator_t`, which previously failed to compile for object types without a
-  `key_compare` member type, in version 3.13.0.
@@ -18,11 +18,7 @@ To store objects in C++, a type is defined by the template parameters described
 ## Template parameters

 `ObjectType`
-:   the container to store objects. Its template parameters must have the same order and meaning as those of
-    `std::map`; in particular, the third parameter is a comparator. `#!cpp std::unordered_map`, whose third parameter
-    is a hash function, therefore needs an adapter -- see
-    [Template Parameter Requirements](../../features/types/template_parameters.md#objecttype) for the full list of
-    requirements, an adapter example, and the containers that are known to work.
+:   the container to store objects (e.g., `std::map` or `std::unordered_map`)

 `StringType`
 :   the type of the keys or names (e.g., `std::string`). The comparison function `std::less<StringType>` is used to
@@ -126,4 +122,3 @@ the object is silently converted as an array of key-value pairs, which is incorr
 ## Version history

 - Added in version 1.0.0.
- Allowed object types whose `erase(iterator)` returns `#!cpp void` in version 3.13.0.
@@ -103,10 +103,6 @@ A UTF-8 byte order mark is silently ignored.
 Invalid Unicode escapes and unpaired surrogates in the input are reported as
 [`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101) with a detailed message.

-By default, a `'\0'` (NUL) byte anywhere in the input is treated as end of input, rather than as an ordinary (and,
-outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-bytes-in-the-input) for details and the
-[`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) macro to opt into rejecting it instead.
-
 ## Examples

 ??? example "Parsing from a character array"
@@ -240,8 +236,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
 - [accept](accept.md) - check if the input is valid JSON
 - [sax_parse](sax_parse.md) - parse input using the SAX interface
 - [operator>>](../operator_gtgt.md) - deserialize from stream
- [`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
-  instead of treating it as end of input

 ## Version history

@@ -252,8 +246,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
 - Added `ignore_trailing_commas` in version 3.13.0.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
- `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
-  it as end of input; planned to become the default in version 4.0.0.

 !!! warning "Deprecation"

@@ -69,9 +69,7 @@ The SAX event lister must follow the interface of [`json_sax`](../json_sax/index
     [`input_format_t`](input_format_t.md) for more information

 `strict` (in)
-:   whether the input has to be consumed completely (optional, `#!cpp true` by default); when `#!cpp false` and the
-    input is a `#!cpp std::istream`, the character that terminates a number is consumed unless
-    [`JSON_PRECISE_STREAM_POSITION`](../macros/json_precise_stream_position.md) is defined to `1`; see [`operator>>`](../operator_gtgt.md#notes)
+:   whether the input has to be consumed completely (optional, `#!cpp true` by default)

 `ignore_comments` (in)
 :   whether comments should be ignored and treated like whitespace (`#!cpp true`) or yield a parse error
@@ -138,8 +136,6 @@ A UTF-8 byte order mark is silently ignored.
 - Added `ignore_trailing_commas` in version 3.13.0.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
- `JSON_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave a `#!cpp std::istream` positioned right
-  after the parsed value when `strict` is `#!cpp false`.

 !!! warning "Deprecation"

@@ -23,11 +23,6 @@ JSON class into byte-sized characters during deserialization.
    `StringType`. To work with wide-character data, convert it to/from UTF-8 at the boundary instead -- see the
    FAQ's [wide string handling](../../home/faq.md#wide-string-handling) section for a conversion recipe.

-    Beyond the character type, the library expects a substantial part of the `#!cpp std::string` interface (contiguous
-    null-terminated `data()`, `substr()`, `find()`, `append()`, ...). See
-    [Template Parameter Requirements](../../features/types/template_parameters.md#stringtype) for the full list and
-    for the string types that are known to work.
-
 ## Notes

 #### Default type
@@ -83,5 +78,3 @@ and an example.
 ## Version history

 - Added in version 1.0.0.
- Removed the requirement that `string_t` be implicitly convertible from `#!cpp std::string`, which the BSON writer and
-  the UBJSON reader relied on, in version 3.13.0.
@@ -37,14 +37,7 @@ Linear in the size of the JSON value.
 ## Notes

 Empty objects and arrays are flattened by [`flatten()`](flatten.md) to `#!json null` values and cannot unflattened to
-their original type.
-
-A flattened array and a flattened object whose keys are array indices are indistinguishable, because both are
-described by the same JSON pointers. A value is therefore restored as an array if and only if one of its keys is the
-reference token `0`, and as an object otherwise: `#!json {"2": 1}` is restored unchanged, whereas `#!json {"0": 1}` is
-restored as `#!json [1]`. This decision does not depend on the order in which the flattened object is iterated.
-
-Apart from these two cases, for a JSON value `j`, the following is always true:
+their original type. Apart from this example, for a JSON value `j`, the following is always true:
 `#!cpp j == j.flatten().unflatten()`.

 ## Examples
@@ -70,4 +63,3 @@ Apart from these two cases, for a JSON value `j`, the following is always true:
 ## Version history

 - Added in version 2.0.0.
- Made the array/object decision independent of the object's iteration order in version 3.13.0.
@@ -14,13 +14,6 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_DIAGNOSTIC_POSITIONS**](json_diagnostic_positions.md) - access positions of elements
 - [**JSON_NOEXCEPTION**](json_noexception.md) - switch off exceptions

-## Parsing
-
- [**JSON_PRECISE_STREAM_POSITION**](json_precise_stream_position.md) - opt in to leaving an input stream positioned
-  right after a parsed number
- [**JSON_STRICT_NUL_HANDLING**](json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input instead of
-  treating it as end of input
-
 ## Language support

 - [**JSON_HAS_CPP_11**<br>**JSON_HAS_CPP_14**<br>**JSON_HAS_CPP_17**<br>**JSON_HAS_CPP_20**](json_has_cpp_11.md) - set supported C++ standard
@@ -29,7 +22,6 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_HAS_STD_FORMAT**](json_has_std_format.md) - control `std::format`/`std::formatter` support
 - [**JSON_HAS_THREE_WAY_COMPARISON**](json_has_three_way_comparison.md) - control 3-way comparison support
 - [**JSON_NO_IO**](json_no_io.md) - switch off functions relying on certain C++ I/O headers
- [**JSON_NO_THREAD_LOCAL**](json_no_thread_local.md) - switch off the use of `thread_local` storage
 - [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](json_skip_unsupported_compiler_check.md) - do not warn about unsupported compilers
 - [**JSON_USE_GLOBAL_UDLS**](json_use_global_udls.md) - place user-defined string literals (UDLs) into the global namespace
 - [**JSON_USE_SIMDUTF**](json_use_simdutf.md) - use the simdutf library to accelerate UTF-8 validation
@@ -38,28 +38,6 @@ The default value is `0` (disabled — existing behavior is preserved).

    This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no effect.

-!!! warning "Applies to every single-element list"
-
-    The macro does not only affect a single JSON value in braces. **Any** single-element braced list is treated as its
-    element, so it no longer creates a one-element array:
-
-    ```cpp
-    json j1 = {1};       // 1, not [1]
-    json j2 = {"text"};  // "text", not ["text"]
-    json j3 = {{1, 2}};  // [1,2], not [[1,2]]
-    ```
-
-    Code that relies on these producing arrays must use `json::array()` instead (see below). Lists with more than one
-    element, and a single `[string, value]` pair such as `{{"key", "value"}}`, which still creates an object, are not
-    affected. The library's own conversions are not affected either: for example, `std::tuple<int>{5}` still becomes
-    `[5]`.
-
-!!! note "ABI compatibility"
-
-    The value of this macro is encoded in the [namespace](../../features/namespace.md) (tag `_bics`), resulting in
-    distinct symbol names. Translation units compiled with and without it can therefore be linked into the same program
-    without One Definition Rule (ODR) violations, but they cannot exchange instances of library types.
-
 !!! tip "Workaround without the macro"

    To explicitly create a single-element array without enabling this macro, use `json::array()`:
@@ -1,48 +0,0 @@
-# JSON_NO_THREAD_LOCAL
-
-```cpp
-#define JSON_NO_THREAD_LOCAL
-```
-
-When defined, the library does not use `#!cpp thread_local` storage. This is relevant for the few environments whose
-toolchain does not support it.
-
-Copying a value and comparing two values both descend into the first levels by letting the containers copy or compare
-themselves, and finish whatever is nested deeper than that without the call stack, so that neither can exhaust the stack
-however deeply the values are nested. Each counts the levels it has descended into in a `#!cpp thread_local` variable, as
-a counter shared between threads would be raced.
-
-Without those counters, no descent can be bounded safely, so objects and arrays are copied and compared without the call
-stack right away. Both keep working exactly as they do otherwise - the same values come out, the same comparisons hold,
-and deeply nested values are handled just as safely - but both are slower, because the containers no longer copy or
-compare themselves. Copying the benchmark documents takes 9% (`canada.json`) to 34% (`twitter.json`) longer, and
-comparing two equal ones 10% (`citm_catalog.json`) to 90% (`canada.json`) longer.
-
-## Default definition
-
-By default, `#!cpp JSON_NO_THREAD_LOCAL` is not defined.
-
-```cpp
-#undef JSON_NO_THREAD_LOCAL
-```
-
-The library defines it by itself for Clang targeting MinGW, which does not survive the `#!cpp thread_local` storage:
-copying a value segfaults there, with both old and current Clang versions, while GCC targeting MinGW is unaffected.
-Copying and comparing fall back to working without the call stack there, as they do whenever the macro is defined.
-
-## Examples
-
-??? example
-
-    The code below forces the library not to use `#!cpp thread_local` storage.
-
-    ```cpp
-    #define JSON_NO_THREAD_LOCAL 1
-    #include <nlohmann/json.hpp>
-
-    ...
-    ```
-
-## Version history
-
- Added in version 3.12.1.
@@ -1,131 +0,0 @@
-# JSON_PRECISE_STREAM_POSITION
-
-```cpp
-#define JSON_PRECISE_STREAM_POSITION /* value */
-```
-
-When defined to `1`, [`operator>>`](../operator_gtgt.md) and [`sax_parse`](../basic_json/sax_parse.md) with
-`strict = false` leave a `#!cpp std::istream` positioned right after the parsed value for every value type. By default,
-the character that terminates a number is consumed as well.
-
-The macro only affects reading from a `#!cpp std::istream` when the rest of the stream is not required to be consumed.
-[`parse`](../basic_json/parse.md), [`accept`](../basic_json/accept.md), and all other inputs (strings, iterators,
-containers, `#!cpp FILE*`) are never affected.
-
-## Default definition
-
-The default value is `0` (disabled — existing behavior is preserved).
-
-```cpp
-#define JSON_PRECISE_STREAM_POSITION 0
-```
-
-## Notes
-
-!!! note "Background"
-
-    A number is the only JSON value whose end can be detected solely by reading the character that follows it. By
-    default, that character is consumed and not put back, so the stream is left one byte too far after a number, and
-    only after a number:
-
-    ```cpp
-    std::istringstream input("1true");
-    json j;
-    input >> j;  // j == 1, but the stream now starts at "rue"
-    ```
-
-    With this macro, the character is only looked at and left in the stream, so the stream starts at `true`. This
-    does not require the stream buffer to support putting a character back.
-
-    This was not changed unconditionally, because code can depend on the consumed character, even unknowingly (see
-    [#5340](https://github.com/nlohmann/json/issues/5340)). Both of the following work by default only because the
-    character after each number is swallowed, and behave differently with this macro:
-
-    ```cpp
-    std::istringstream input("1,2,3");
-    json j1, j2, j3;
-    input >> j1 >> j2 >> j3;  // default: 1, 2, 3
-                              // with the macro: throws parse_error.101 at the ','
-    ```
-
-    ```cpp
-    std::istringstream input("42\nfoo");
-    json j;
-    std::string line;
-    input >> j;
-    std::getline(input, line);  // default: "foo"
-                                // with the macro: "" (like after reading an int with >>)
-    ```
-
-    In both cases, the behavior with the macro is what you already get today when the value is not a number: `"a","b"`
-    fails at the `,`, and `std::getline` after `{}` returns an empty string. This macro offers an opt-in path to
-    the consistent behavior ahead of version 4.0.0, where it is planned to become the default.
-
-!!! warning "Opt-in only"
-
-    This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no
-    effect.
-
-!!! note "ABI compatibility"
-
-    The value of this macro is encoded in the [namespace](../../features/namespace.md) (tag `_psp`), resulting in
-    distinct symbol names. Translation units compiled with and without it can therefore be linked into the same program
-    without One Definition Rule (ODR) violations, but they cannot exchange instances of library types.
-
-!!! tip "Workaround without the macro"
-
-    Separate the values in the stream with whitespace. The character consumed after a number is then the separator,
-    and whitespace before the next value is skipped anyway.
-
-## Examples
-
-??? example "Default behavior (macro not defined)"
-
-    Without the macro, the character after a number is consumed:
-
-    ```cpp
-    #include <iostream>
-    #include <sstream>
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        std::istringstream input("1true");
-        json j1, j2;
-        input >> j1;  // j1 == 1
-        input >> j2;  // throws parse_error.101: the stream now starts at "rue"
-    }
-    ```
-
-??? example "Opt-in precise stream position (macro defined to 1)"
-
-    With the macro, the stream is positioned right after the number:
-
-    ```cpp
-    #define JSON_PRECISE_STREAM_POSITION 1
-    #include <iostream>
-    #include <sstream>
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        std::istringstream input("1true");
-        json j1, j2;
-        input >> j1;  // j1 == 1
-        input >> j2;  // j2 == true
-    }
-    ```
-
-## See also
-
- [**operator>>**](../operator_gtgt.md) - deserialize from stream
- [**sax_parse**](../basic_json/sax_parse.md) - generate SAX events
-
-## Version history
-
- Added in version 3.13.0.
- Planned to become the default (with the macro removed) in version 4.0.0.
@@ -1,126 +0,0 @@
-# JSON_STRICT_NUL_HANDLING
-
-```cpp
-#define JSON_STRICT_NUL_HANDLING /* value */
-```
-
-When defined to `1`, a `'\0'` (NUL) byte in JSON text input is rejected with `parse_error.101`, like any other
-unexpected byte, instead of being silently treated as end of input.
-
-The macro only affects the JSON text parser ([`parse`](../basic_json/parse.md), [`accept`](../basic_json/accept.md),
-[`sax_parse`](../basic_json/sax_parse.md), and [`operator>>`](../operator_gtgt.md)). There are three cases where a NUL
-byte is still not rejected:
-
- The binary formats ([`from_bjdata`](../basic_json/from_bjdata.md), [`from_bson`](../basic_json/from_bson.md),
-  [`from_cbor`](../basic_json/from_cbor.md), [`from_msgpack`](../basic_json/from_msgpack.md),
-  [`from_ubjson`](../basic_json/from_ubjson.md)) are never affected: there, `0x00` is ordinary data.
- A bare `const char*` pointer has no length of its own, so its length is still determined with `strlen()`. The first
-  NUL byte therefore still marks the end of the input, and nothing after it is read.
- One trailing `'\0'` at the end of a `char` array (e.g., a string literal) is trimmed; see the warning below.
-
-## Default definition
-
-The default value is `0` (disabled — existing behavior is preserved).
-
-```cpp
-#define JSON_STRICT_NUL_HANDLING 0
-```
-
-## Notes
-
-!!! note "Background"
-
-    By default, a `'\0'` byte anywhere in the input is treated the same as the real end of the input, rather than as
-    an ordinary (and, outside of a string, invalid) byte. Everything from that byte onward is silently ignored,
-    without a parse error - including further, otherwise well-formed JSON:
-
-    ```cpp
-    json::parse(std::string("123") + '\0');          // == 123, no error
-    json::parse(std::string("123") + '\0' + "true"); // == 123, the "true" is silently ignored too
-    ```
-
-    This falls out of the same convention used when no explicit input length is given at all: parsing from a
-    `const char*` already stops at the first NUL byte via `strlen()`, since a bare pointer has no length of its own.
-    The library applies that same NUL-terminated-C-string convention uniformly, rather than only when a length is
-    genuinely unavailable - so a `std::string`, iterator range, or container whose content happens to include a NUL
-    byte is affected the same way a raw `const char*` would be (see the
-    [FAQ entry](../../home/faq.md#nul-bytes-in-the-input) for a fuller explanation).
-
-    This was not fixed unconditionally, because doing so is backwards-incompatible for any caller who happens to
-    depend on the current behavior - even unknowingly, for instance because their input already contains trailing
-    padding they never noticed was being discarded (see [#5530](https://github.com/nlohmann/json/issues/5530)).
-    This macro instead offers an opt-in path to the corrected behavior ahead of version 4.0.0, where it is planned to
-    become the default.
-
-!!! warning "Opt-in only"
-
-    This macro must be defined **before** including `<nlohmann/json.hpp>`. Defining it after the include has no
-    effect.
-
-    Enabling it also changes how a `char` array (including a string literal, e.g. `json::parse("123")`) is read: such
-    an array normally carries a trailing `'\0'` contributed by the compiler, not by the source text. With this macro
-    enabled, that one trailing byte is trimmed if present so that parsing a string literal keeps working; every other
-    byte in the array - including any `'\0'` that is not the very last element - is read as real data and rejected
-    like any other unexpected byte. Arrays of any other element type (`unsigned char`, `std::uint8_t`, ...), as used
-    for CBOR or MessagePack, are never affected by this trimming; their full extent - including a genuine trailing
-    `0x00` - is always preserved, in both states of this macro.
-
-!!! tip "Workaround without the macro"
-
-    To reject a NUL byte without enabling this macro, trim your input yourself before calling `parse()`:
-
-    ```cpp
-    s.resize(s.find('\0')); // drop everything from the first NUL onward, if any
-    json::parse(s);
-    ```
-
-## Examples
-
-??? example "Default behavior (macro not defined)"
-
-    Without the macro, a NUL byte silently ends parsing at that point:
-
-    ```cpp
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        json j = json::parse(std::string("123") + '\0' + "true");
-        // j is 123 -- the '\0' and everything after it is silently ignored
-    }
-    ```
-
-??? example "Opt-in strict handling (macro defined to 1)"
-
-    With the macro, a NUL byte is rejected like any other unexpected byte:
-
-    ```cpp
-    #define JSON_STRICT_NUL_HANDLING 1
-    #include <nlohmann/json.hpp>
-
-    using json = nlohmann::json;
-
-    int main()
-    {
-        json j = json::parse(std::string("123") + '\0' + "true");
-        // throws parse_error.101 -- the NUL byte is now invalid input,
-        // exactly like any other unexpected trailing byte
-
-        json ok = json::parse("123");
-        // ok is 123 -- parsing from a string literal still works
-    }
-    ```
-
-## See also
-
- [FAQ: NUL bytes in the input](../../home/faq.md#nul-bytes-in-the-input)
- [**parse**](../basic_json/parse.md) - deserialize from a compatible input
- [**accept**](../basic_json/accept.md) - check if the input is valid JSON
- [**operator>>**](../operator_gtgt.md) - deserialize from stream
-
-## Version history
-
- Added in version 3.13.0.
- Planned to become the default (with the macro removed) in version 4.0.0.
@@ -12,11 +12,9 @@
 Controls how exceptions are handled by the library.

 1. This macro overrides [`#!cpp catch`](https://en.cppreference.com/w/cpp/language/try_catch) calls inside the library.
-   The argument is the type of the exception to catch. The library uses it in a single place: to swallow any exception
-   escaping the parent-pointer check that [`JSON_DIAGNOSTICS`](json_diagnostics.md) adds to the class invariant. The
-   places where the library catches its own [`json::out_of_range`](../../home/exceptions.md#out-of-range) exceptions
-   use `JSON_INTERNAL_CATCH` instead, which `JSON_CATCH_USER` also overrides unless `JSON_INTERNAL_CATCH_USER` is
-   defined. The macro is always followed by a scope.
+   The argument is the type of the exception to catch. As of version 3.8.0, the library only catches `std::out_of_range`
+   exceptions internally to rethrow them as [`json::out_of_range`](../../home/exceptions.md#out-of-range) exceptions.
+   The macro is always followed by a scope.
 2. This macro overrides `#!cpp throw` calls inside the library. The argument is the exception to be thrown. Note that
   `JSON_THROW_USER` should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield
   undefined behavior.
@@ -24,14 +24,6 @@ By default, implicit conversions are enabled.
    You can prepare existing code by already defining `JSON_USE_IMPLICIT_CONVERSIONS` to `0` and replace any implicit
    conversions with calls to [`get`](../basic_json/get.md).

-!!! tip "Automatic migration"
-
-    The community-maintained clang-tidy check `modernize-nlohmann-json-explicit-conversions` rewrites implicit
-    conversions into explicit calls to [`get`](../basic_json/get.md); for example, `#!cpp int i = j;` becomes
-    `#!cpp int i = j.get<int>();`. The check is not part of clang-tidy itself, and it does not catch every case (for
-    example, constructing a `std::optional` from a JSON value), so review the result. See
-    [discussion #4610](https://github.com/nlohmann/json/discussions/4610) for how to build and use it.
-
 !!! hint "CMake option"

    Implicit conversions can also be controlled with the CMake option
@@ -67,20 +67,11 @@ input >> j2;  // parses the next value
    Only numbers are affected. Values ending in a self-delimiting character do not read past themselves, so
    `truefalse`, `[1][2]`, `{"a":1}{"b":2}`, and `"a""b"` can be read back to back without a separator.

-    Define [`JSON_PRECISE_STREAM_POSITION`](macros/json_precise_stream_position.md) to `1` to leave the terminating character in the stream
-    instead, so that the stream is positioned right after the value for every value type and no separator is
-    needed. This is tracked in [#5340](https://github.com/nlohmann/json/issues/5340).
+    This is tracked in [#5340](https://github.com/nlohmann/json/issues/5340).

 Note that reading concatenated values does **not** work for [JSON Lines](../features/parsing/json_lines.md)
 (newline-delimited JSON) input -- see that page for why and for the recommended alternative.

-By default, a `'\0'` (NUL) byte encountered while reading a value is treated as end of input, rather than as an
-ordinary (and, outside of a string, invalid) byte; see the [FAQ entry](../home/faq.md#nul-bytes-in-the-input) for
-details and the [`JSON_STRICT_NUL_HANDLING`](macros/json_strict_nul_handling.md) macro to opt into rejecting it
-instead. Because `operator>>` only parses a single value and does not require the rest of the stream to be consumed,
-a NUL byte *after* a complete value has no effect on `operator>>` either way; it only matters while a value is still
-being read.
-
 !!! warning "Deprecation"

    This function replaces function `#!cpp std::istream& operator<<(basic_json& j, std::istream& i)` which has
@@ -107,14 +98,7 @@ being read.

 - [accept](basic_json/accept.md) - check if the input is valid JSON
 - [parse](basic_json/parse.md) - deserialize from a compatible input
- [`JSON_STRICT_NUL_HANDLING`](macros/json_strict_nul_handling.md) - opt in to rejecting a NUL byte in the input
-  instead of treating it as end of input
- [`JSON_PRECISE_STREAM_POSITION`](macros/json_precise_stream_position.md) - opt in to leaving the stream positioned right after a number

 ## Version history

 - Added in version 1.0.0.
- `JSON_STRICT_NUL_HANDLING` added in version 3.13.0 to optionally reject a NUL byte in the input instead of treating
-  it as end of input; planned to become the default in version 4.0.0.
- `JSON_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave the character that terminates a number in
-  the stream; planned to become the default in version 4.0.0.
@@ -1,70 +0,0 @@
-# Assurance case
-
-This page argues why the library meets its security requirements. It describes the threats the library faces, where the
-trust boundaries lie, and how the library's design and the [quality assurance](quality_assurance.md) counter these
-threats. To report a vulnerability, see the [security policy](security_policy.md).
-
-## Threat model
-
-The library parses, stores, and serializes JSON values in memory. It does not open network connections, does not open
-files (it only reads from streams or `std::FILE*` handles that the caller has already opened), does not read environment
-variables, and does not implement cryptography or handle credentials.
-
-The primary threat is therefore **untrusted input**: JSON text or binary data (BJData, BSON, CBOR, MessagePack, UBJSON)
-that an attacker controls, passed to [`parse`](../api/basic_json/parse.md), [`accept`](../api/basic_json/accept.md),
-[`sax_parse`](../api/basic_json/sax_parse.md), or one of the `from_*` functions such as
-[`from_cbor`](../api/basic_json/from_cbor.md). Such input may try to
-
- make the library read or write out of bounds (malformed lengths, truncated input, invalid UTF-8),
- trigger undefined behavior (integer overflow in sizes or numbers, invalid casts),
- exhaust memory (huge announced sizes), or
- exhaust the call stack (deeply nested arrays and objects).
-
-## Trust boundaries
-
- **Untrusted:** all serialized input read by the parser, the SAX interface, and the binary readers. The library must
-  handle every possible input by either producing a value or throwing a [`parse_error`](../home/exceptions.md#parse-errors)
-  (or returning `false` when exceptions are disabled for the call).
- **Trusted:** the C++ code that calls the library. Calling a function with violated preconditions, for instance
-  accessing an array with [`operator[]`](../api/basic_json/operator%5B%5D.md) out of range, is a programming error and
-  not a security boundary. Such preconditions are checked with [runtime assertions](../features/assertions.md) in debug
-  builds; functions such as [`at`](../api/basic_json/at.md) offer checked access with exceptions.
-
-## Secure design
-
- **Strict parsing.** The parser accepts exactly the JSON grammar of [RFC 8259](https://datatracker.ietf.org/doc/html/rfc8259).
-  Extensions such as [comments](../features/comments.md) and [trailing commas](../features/trailing_commas.md) must be
-  enabled explicitly. Invalid UTF-8 is rejected.
- **Errors are reported, not ignored.** Malformed input results in a [`parse_error`](../home/exceptions.md#parse-errors)
-  with the byte position of the error. Binary readers do not trust announced sizes: strings and binary values grow
-  only as bytes are actually read, arrays reserve at most a fixed number of elements up front, and sizes that no
-  container can hold are rejected.
- **Memory is owned by values.** Each `basic_json` value owns its content, and there is no manual memory management in
-  user code. The destructor does not recurse, so destroying a deeply nested value does not exhaust the stack.
- **Bounded recursion.** The JSON parser and the binary readers keep their state in explicit stacks instead of
-  recursing per nesting level. Operations that walk a value, such as [`dump`](../api/basic_json/dump.md), copying,
-  hashing, and [`merge_patch`](../api/basic_json/merge_patch.md), recurse only up to a fixed depth and continue with an
-  explicit stack below it. Some operations, such as comparison, [`diff`](../api/basic_json/diff.md),
-  [`flatten`](../api/basic_json/flatten.md), and the binary writers, still recurse once per nesting level; work on them
-  is in progress. Applications that process untrusted input can limit its nesting depth with a
-  [parser callback](../features/parsing/parser_callbacks.md).
- **Invariants are checked.** The class invariant (for instance, that the pointer for the stored type is never null) is
-  checked with runtime assertions throughout the test suite.
-
-## Common weaknesses
-
-The following table maps the relevant classes of the [Common Weakness Enumeration](https://cwe.mitre.org) to the
-measures that counter them. The measures are described in detail in [Quality assurance](quality_assurance.md).
-
-| Weakness                                                                  | Countermeasures                                                                                  |
-|---------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------|
-| Out-of-bounds read/write ([CWE-125](https://cwe.mitre.org/data/definitions/125.html), [CWE-787](https://cwe.mitre.org/data/definitions/787.html)) | bounds checks on all reads from the input; AddressSanitizer and Valgrind on the test suite; OSS-Fuzz      |
-| Integer overflow ([CWE-190](https://cwe.mitre.org/data/definitions/190.html)) | UndefinedBehaviorSanitizer with integer overflow detection; Clang-Tidy; Cppcheck                 |
-| Use after free, double free ([CWE-416](https://cwe.mitre.org/data/definitions/416.html), [CWE-415](https://cwe.mitre.org/data/definitions/415.html)) | ownership of all memory by values; AddressSanitizer and Valgrind; Clang Static Analyzer          |
-| Memory leaks ([CWE-401](https://cwe.mitre.org/data/definitions/401.html)) | Valgrind (Memcheck) on the test suite                                                            |
-| Uncontrolled recursion ([CWE-674](https://cwe.mitre.org/data/definitions/674.html)) | iterative parser, binary readers, and destructor; bounded recursion in value operations; tests with deeply nested inputs |
-| Uncontrolled resource consumption ([CWE-400](https://cwe.mitre.org/data/definitions/400.html)) | allocations based on announced sizes are capped; OSS-Fuzz with memory limits                     |
-| Undefined behavior in general ([CWE-758](https://cwe.mitre.org/data/definitions/758.html)) | UndefinedBehaviorSanitizer; runtime assertions; Clang-Tidy, Cppcheck, Clang Static Analyzer, Infer |
-
-In addition, every line of the library is covered by the unit tests, and all parsers are fuzz-tested around the clock
-by [OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json).
@@ -5,6 +5,4 @@
 - [Contribution Guidelines](contribution_guidelines.md) - guidelines how to contribute to this project
 - [Governance](governance.md) - the governance model of this project
 - [Quality Assurance](quality_assurance.md) - how the quality of this project is assured
- [Roadmap](roadmap.md) - what the project will and will not do
 - [Security Policy](security_policy.md) - the security policy of the project
- [Assurance Case](assurance_case.md) - why the library meets its security requirements
@@ -164,9 +164,6 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
 - [x] The parser is tested against extensive correctness suites for JSON compliance.
 - [x] In addition, the library is continuously fuzz-tested at [OSS-Fuzz](https://google.github.io/oss-fuzz/) where the
  library is checked against billions of inputs.
- [x] Every crash reported by OSS-Fuzz is fixed together with a unit test that reproduces it, and the fix references
-  the OSS-Fuzz issue. The round-trip checks of the fuzzer drivers are also part of the unit tests. See the
-  [fuzz testing documentation](https://github.com/nlohmann/json/blob/develop/tests/fuzzing.md#handling-oss-fuzz-reports).

 ## Static analysis

@@ -1,43 +0,0 @@
-# Roadmap
-
-This page describes what the project intends to do, and what it does not intend to do, over the next year. Concrete
-work items are tracked in the [GitHub milestones](https://github.com/nlohmann/json/milestones) and the
-[issue tracker](https://github.com/nlohmann/json/issues).
-
-## What the project will do
-
- **Keep the C++11 baseline.** The library will continue to compile with every
-  [supported C++11 compiler](https://github.com/nlohmann/json/blob/develop/README.md#supported-compilers). Features of
-  later standards are only used when they are guarded by the `JSON_HAS_CPP_*` macros.
- **Stay conformant to JSON.** The parser and serializer follow [RFC 8259](https://datatracker.ietf.org/doc/html/rfc8259).
-  Extensions such as [comments](../features/comments.md) or [trailing commas](../features/trailing_commas.md) remain
-  opt-in.
- **Keep the 3.x public API stable.** Releases follow [semantic versioning](https://semver.org). Changes that would
-  break existing code are only added behind a feature macro, so users can opt in and test their code before a next
-  major release.
- **Support a broad range of compilers and platforms.** The [CI](quality_assurance.md) keeps testing old and new
-  versions of GCC, Clang, MSVC, and other compilers on Linux, macOS, and Windows.
- **Keep the quality assurance up.** Every change keeps the test coverage at 100%, passes the static and dynamic
-  analysis, and is fuzz-tested by OSS-Fuzz, see [Quality assurance](quality_assurance.md).
- **Harden the library against hostile input.** Handling deeply nested values without exhausting the call stack is
-  ongoing work.
- **Fix bugs and security issues** reported through the issue tracker and the [security policy](security_policy.md).
-
-## What the project will not do
-
- **Break the public API of version 3.x.** See the
-  [contribution guidelines](https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#break-the-public-api)
-  for what counts as a breaking change.
- **Require a newer C++ standard than C++11.**
- **Break JSON conformance** or enable non-standard extensions by default.
- **Add dependencies** or require a build step. The library remains header-only, and the single header
-  `json.hpp` remains a complete distribution.
- **Trade simplicity for speed or memory efficiency.** Performance improvements are welcome, but the library is not
-  meant to compete with the fastest JSON libraries, see [Design goals](../home/design_goals.md).
-
-## Version 4.0
-
-There is no decision yet on whether or when a version 4.0 with breaking changes will be released. Proposals that need
-a major version, for instance stricter type conversions, are collected in issue
-[#3453](https://github.com/nlohmann/json/issues/3453). Until then, such changes are only added as opt-in behavior
-behind feature macros.
@@ -1,19 +0,0 @@
-#include <iostream>
-#include <map>
-
-#include <nlohmann/json.hpp>
-
-#include "custom_array_type.hpp"
-
-using custom_json = nlohmann::basic_json<std::map, custom_array_type>;
-
-int main()
-{
-    custom_json j = custom_json::array();
-    j.push_back(1);
-    j.push_back(2);
-    j.push_back(3);
-
-    std::cout << j.dump() << std::endl;
-    std::cout << std::boolalpha << (custom_json::parse(j.dump()) == j) << std::endl;
-}
@@ -1,152 +0,0 @@
-#pragma once
-
-#include <memory>
-#include <utility>
-#include <vector>
-
-// A minimal, self-contained ArrayType built around a private std::vector.
-// See https://json.nlohmann.me/features/types/template_parameters/#arraytype
-template<class T, class Allocator = std::allocator<T>>
-class custom_array_type
-{
-    using vector_t = std::vector<T, Allocator>;
-    vector_t data_;
-
-  public:
-    using value_type = typename vector_t::value_type;
-    using size_type = typename vector_t::size_type;
-    using iterator = typename vector_t::iterator;
-    using const_iterator = typename vector_t::const_iterator;
-
-    custom_array_type() = default;
-    custom_array_type(const custom_array_type&) = default;
-    custom_array_type(custom_array_type&&) = default;
-    custom_array_type& operator=(const custom_array_type&) = default;
-    custom_array_type& operator=(custom_array_type&&) = default;
-
-    template<class InputIt>
-    custom_array_type(InputIt first, InputIt last) : data_(first, last) {}
-
-    custom_array_type(size_type count, const T& value) : data_(count, value) {}
-
-    iterator begin()
-    {
-        return data_.begin();
-    }
-    iterator end()
-    {
-        return data_.end();
-    }
-    const_iterator begin() const
-    {
-        return data_.begin();
-    }
-    const_iterator end() const
-    {
-        return data_.end();
-    }
-    const_iterator cbegin() const
-    {
-        return data_.cbegin();
-    }
-    const_iterator cend() const
-    {
-        return data_.cend();
-    }
-
-    bool empty() const
-    {
-        return data_.empty();
-    }
-    size_type size() const
-    {
-        return data_.size();
-    }
-    size_type max_size() const
-    {
-        return data_.max_size();
-    }
-    void clear()
-    {
-        data_.clear();
-    }
-    void resize(size_type n)
-    {
-        data_.resize(n);
-    }
-
-    T& operator[](size_type pos)
-    {
-        return data_[pos];
-    }
-    const T& operator[](size_type pos) const
-    {
-        return data_[pos];
-    }
-
-    T& back()
-    {
-        return data_.back();
-    }
-    const T& back() const
-    {
-        return data_.back();
-    }
-
-    void push_back(const T& value)
-    {
-        data_.push_back(value);
-    }
-    void push_back(T&& value)
-    {
-        data_.push_back(std::move(value));
-    }
-
-    template<class... Args>
-    void emplace_back(Args&& ... args)
-    {
-        data_.emplace_back(std::forward<Args>(args)...);
-    }
-
-    void pop_back()
-    {
-        data_.pop_back();
-    }
-
-    iterator insert(const_iterator pos, const T& value)
-    {
-        return data_.insert(pos, value);
-    }
-    iterator insert(const_iterator pos, size_type count, const T& value)
-    {
-        return data_.insert(pos, count, value);
-    }
-    template<class InputIt>
-    iterator insert(const_iterator pos, InputIt first, InputIt last)
-    {
-        return data_.insert(pos, first, last);
-    }
-
-    iterator erase(const_iterator pos)
-    {
-        return data_.erase(pos);
-    }
-    iterator erase(const_iterator first, const_iterator last)
-    {
-        return data_.erase(first, last);
-    }
-
-    void swap(custom_array_type& other)
-    {
-        data_.swap(other.data_);
-    }
-
-    friend bool operator==(const custom_array_type& lhs, const custom_array_type& rhs)
-    {
-        return lhs.data_ == rhs.data_;
-    }
-    friend bool operator<(const custom_array_type& lhs, const custom_array_type& rhs)
-    {
-        return lhs.data_ < rhs.data_;
-    }
-};
@@ -1,2 +0,0 @@
-[1,2,3]
-true
@@ -1,21 +0,0 @@
-#include <cstdint>
-#include <iostream>
-#include <map>
-#include <string>
-#include <vector>
-
-#include <nlohmann/json.hpp>
-
-#include "custom_binary_type.hpp"
-
-using custom_json = nlohmann::basic_json<std::map, std::vector, std::string, bool,
-      std::int64_t, std::uint64_t, double, std::allocator,
-      nlohmann::adl_serializer, custom_binary_type>;
-
-int main()
-{
-    const auto j = custom_json::binary({0x01, 0x02, 0x03});
-
-    std::cout << j.dump() << std::endl;
-    std::cout << std::boolalpha << (custom_json::from_cbor(custom_json::to_cbor(j)) == j) << std::endl;
-}
@@ -1,112 +0,0 @@
-#pragma once
-
-#include <cstdint>
-#include <initializer_list>
-#include <vector>
-
-// A minimal, self-contained BinaryType built around a private std::vector.
-// See https://json.nlohmann.me/features/types/template_parameters/#binarytype
-class custom_binary_type
-{
-    using vector_t = std::vector<std::uint8_t>;
-    vector_t data_;
-
-  public:
-    using value_type = vector_t::value_type;
-    using size_type = vector_t::size_type;
-    using iterator = vector_t::iterator;
-    using const_iterator = vector_t::const_iterator;
-
-    custom_binary_type() = default;
-    custom_binary_type(const custom_binary_type&) = default;
-    custom_binary_type(custom_binary_type&&) = default;
-    custom_binary_type& operator=(const custom_binary_type&) = default;
-    custom_binary_type& operator=(custom_binary_type&&) = default;
-
-    template<class InputIt>
-    custom_binary_type(InputIt first, InputIt last) : data_(first, last) {}
-
-    // so basic_json::binary({0x01, 0x02}) can build one directly
-    custom_binary_type(std::initializer_list<std::uint8_t> init) : data_(init) {}
-
-    size_type size() const
-    {
-        return data_.size();
-    }
-    bool empty() const
-    {
-        return data_.empty();
-    }
-    void clear()
-    {
-        data_.clear();
-    }
-    void resize(size_type n)
-    {
-        data_.resize(n);
-    }
-
-    // read-only is enough: the writers only ever read from a binary value
-    const std::uint8_t* data() const
-    {
-        return data_.data();
-    }
-
-    std::uint8_t& operator[](size_type pos)
-    {
-        return data_[pos];
-    }
-    std::uint8_t operator[](size_type pos) const
-    {
-        return data_[pos];
-    }
-
-    std::uint8_t& back()
-    {
-        return data_.back();
-    }
-    std::uint8_t back() const
-    {
-        return data_.back();
-    }
-
-    iterator begin()
-    {
-        return data_.begin();
-    }
-    iterator end()
-    {
-        return data_.end();
-    }
-    const_iterator begin() const
-    {
-        return data_.begin();
-    }
-    const_iterator end() const
-    {
-        return data_.end();
-    }
-    const_iterator cbegin() const
-    {
-        return data_.cbegin();
-    }
-    const_iterator cend() const
-    {
-        return data_.cend();
-    }
-
-    template<class InputIt>
-    iterator insert(const_iterator pos, InputIt first, InputIt last)
-    {
-        return data_.insert(pos, first, last);
-    }
-
-    friend bool operator==(const custom_binary_type& lhs, const custom_binary_type& rhs)
-    {
-        return lhs.data_ == rhs.data_;
-    }
-    friend bool operator<(const custom_binary_type& lhs, const custom_binary_type& rhs)
-    {
-        return lhs.data_ < rhs.data_;
-    }
-};
@@ -1,2 +0,0 @@
-{"bytes":[1,2,3],"subtype":null}
-true
@@ -1,26 +0,0 @@
-#include <iostream>
-#include <type_traits>
-#include <vector>
-
-#include <nlohmann/json.hpp>
-
-#include "custom_object_type.hpp"
-
-using custom_json = nlohmann::basic_json<custom_object_type, std::vector>;
-
-int main()
-{
-    custom_json j;
-    j["pi"] = 3.141;
-    j["happy"] = true;
-    j["list"] = {1, 2, 3};
-
-    std::cout << j.dump(2) << std::endl;
-    std::cout << std::boolalpha << (custom_json::parse(j.dump()) == j) << std::endl;
-
-    // custom_object_type has no key_compare member, so object_comparator_t
-    // falls back to its default
-    std::cout << std::boolalpha
-              << std::is_same<custom_json::object_comparator_t, custom_json::default_object_comparator_t>::value
-              << std::endl;
-}
@@ -1,144 +0,0 @@
-#pragma once
-
-#include <map>
-#include <utility>
-
-// A minimal, self-contained ObjectType built around a private std::map.
-// key_compare is deliberately not exposed: when an ObjectType has no
-// key_compare member, the library falls back to its own default comparator.
-// See https://json.nlohmann.me/features/types/template_parameters/#objecttype
-template<class Key, class T, class Compare, class Allocator>
-class custom_object_type
-{
-    using map_t = std::map<Key, T, Compare, Allocator>;
-    map_t data_;
-
-  public:
-    using key_type = typename map_t::key_type;
-    using mapped_type = typename map_t::mapped_type;
-    using value_type = typename map_t::value_type;
-    using size_type = typename map_t::size_type;
-    using iterator = typename map_t::iterator;
-    using const_iterator = typename map_t::const_iterator;
-
-    custom_object_type() = default;
-    custom_object_type(const custom_object_type&) = default;
-    custom_object_type(custom_object_type&&) = default;
-    custom_object_type& operator=(const custom_object_type&) = default;
-    custom_object_type& operator=(custom_object_type&&) = default;
-
-    template<class InputIt>
-    custom_object_type(InputIt first, InputIt last) : data_(first, last) {}
-
-    iterator begin()
-    {
-        return data_.begin();
-    }
-    iterator end()
-    {
-        return data_.end();
-    }
-    const_iterator begin() const
-    {
-        return data_.begin();
-    }
-    const_iterator end() const
-    {
-        return data_.end();
-    }
-    const_iterator cbegin() const
-    {
-        return data_.cbegin();
-    }
-    const_iterator cend() const
-    {
-        return data_.cend();
-    }
-
-    bool empty() const
-    {
-        return data_.empty();
-    }
-    size_type size() const
-    {
-        return data_.size();
-    }
-    size_type max_size() const
-    {
-        return data_.max_size();
-    }
-    void clear()
-    {
-        data_.clear();
-    }
-
-    iterator find(const key_type& key)
-    {
-        return data_.find(key);
-    }
-    const_iterator find(const key_type& key) const
-    {
-        return data_.find(key);
-    }
-    size_type count(const key_type& key) const
-    {
-        return data_.count(key);
-    }
-
-    std::pair<iterator, bool> emplace(const key_type& key, const mapped_type& value)
-    {
-        return data_.emplace(key, value);
-    }
-
-    std::pair<iterator, bool> insert(const value_type& value)
-    {
-        return data_.insert(value);
-    }
-
-    template<class InputIt>
-    void insert(InputIt first, InputIt last)
-    {
-        data_.insert(first, last);
-    }
-
-    mapped_type& operator[](const key_type& key)
-    {
-        return data_[key];
-    }
-
-    mapped_type& at(const key_type& key)
-    {
-        return data_.at(key);
-    }
-    const mapped_type& at(const key_type& key) const
-    {
-        return data_.at(key);
-    }
-
-    iterator erase(iterator pos)
-    {
-        return data_.erase(pos);
-    }
-    iterator erase(iterator first, iterator last)
-    {
-        return data_.erase(first, last);
-    }
-    size_type erase(const key_type& key)
-    {
-        return data_.erase(key);
-    }
-
-    void swap(custom_object_type& other)
-    {
-        data_.swap(other.data_);
-    }
-
-    friend bool operator==(const custom_object_type& lhs, const custom_object_type& rhs)
-    {
-        return lhs.data_ == rhs.data_;
-    }
-    friend bool operator<(const custom_object_type& lhs, const custom_object_type& rhs)
-    {
-        return lhs.data_ < rhs.data_;
-    }
-};
@@ -1,11 +0,0 @@
-{
-  "happy": true,
-  "list": [
-    1,
-    2,
-    3
-  ],
-  "pi": 3.141
-}
-true
-true
@@ -1,20 +0,0 @@
-#include <iostream>
-#include <map>
-#include <vector>
-
-#include <nlohmann/json.hpp>
-
-#include "custom_string_type.hpp"
-
-using custom_json = nlohmann::basic_json<std::map, std::vector, custom_string_type>;
-
-int main()
-{
-    custom_json j;
-    j["pi"] = 3.141;
-    j["happy"] = true;
-    j["list"] = {1, 2, 3};
-
-    std::cout << j.dump(2) << std::endl;
-    std::cout << std::boolalpha << (custom_json::parse(j.dump()) == j) << std::endl;
-}
@@ -1,134 +0,0 @@
-#pragma once
-
-#include <ostream>
-#include <string>
-
-// A minimal, self-contained StringType built around a private std::string.
-// Wraps rather than inherits, so it exposes exactly what the library needs
-// and nothing more of std::string's interface.
-//
-// Covers the "Always required" members, the extras needed for the binary
-// formats, and the extras needed for JSON Pointer / flatten / unflatten /
-// diff. Extending it further (e.g. for std::hash<basic_json> or to_bson) is
-// a matter of adding the extra members listed in the "Required for other
-// functionality" table.
-//
-// See https://json.nlohmann.me/features/types/template_parameters/#stringtype
-class custom_string_type
-{
-    std::string data_;
-
-  public:
-    using value_type = char;
-    using size_type = std::string::size_type;
-    using iterator = std::string::iterator;
-    using const_iterator = std::string::const_iterator;
-
-    static constexpr size_type npos = std::string::npos;
-
-    custom_string_type() = default;
-    custom_string_type(const custom_string_type&) = default;
-    custom_string_type(custom_string_type&&) = default;
-    custom_string_type& operator=(const custom_string_type&) = default;
-    custom_string_type& operator=(custom_string_type&&) = default;
-
-    // not explicit: the library relies on being able to hand it a string literal
-    custom_string_type(const char* s) : data_(s) {}
-    custom_string_type(const char* s, size_type count) : data_(s, count) {}
-    custom_string_type(size_type count, char ch) : data_(count, ch) {}
-
-    size_type size() const
-    {
-        return data_.size();
-    }
-    bool empty() const
-    {
-        return data_.empty();
-    }
-    void clear()
-    {
-        data_.clear();
-    }
-    void resize(size_type n)
-    {
-        data_.resize(n);
-    }
-    void resize(size_type n, char c)
-    {
-        data_.resize(n, c);
-    }
-    void reserve(size_type n)
-    {
-        data_.reserve(n);
-    }
-
-    // must stay null-terminated -- the parser hands this to std::strtoull &
-    // friends; std::string::data() has guaranteed that since C++11
-    const char* data() const
-    {
-        return data_.data();
-    }
-
-    void push_back(char c)
-    {
-        data_.push_back(c);
-    }
-
-    char& operator[](size_type pos)
-    {
-        return data_[pos];
-    }
-    char operator[](size_type pos) const
-    {
-        return data_[pos];
-    }
-
-    custom_string_type& append(const char* s, size_type count)
-    {
-        data_.append(s, count);
-        return *this;
-    }
-    custom_string_type& append(const custom_string_type& other)
-    {
-        data_.append(other.data_);
-        return *this;
-    }
-
-    size_type find_first_of(char c, size_type pos = 0) const
-    {
-        return data_.find_first_of(c, pos);
-    }
-
-    iterator begin()
-    {
-        return data_.begin();
-    }
-    iterator end()
-    {
-        return data_.end();
-    }
-    const_iterator begin() const
-    {
-        return data_.begin();
-    }
-    const_iterator end() const
-    {
-        return data_.end();
-    }
-
-    friend bool operator==(const custom_string_type& lhs, const custom_string_type& rhs)
-    {
-        return lhs.data_ == rhs.data_;
-    }
-    friend bool operator<(const custom_string_type& lhs, const custom_string_type& rhs)
-    {
-        return lhs.data_ < rhs.data_;
-    }
-
-    // not required by the library itself, but dump() returns a custom_string_type
-    // and this makes `std::cout << j.dump()` work as expected
-    friend std::ostream& operator<<(std::ostream& os, const custom_string_type& s)
-    {
-        return os << s.data_;
-    }
-};
@@ -1,10 +0,0 @@
-{
-  "happy": true,
-  "list": [
-    1,
-    2,
-    3
-  ],
-  "pi": 3.141
-}
-true
@@ -116,22 +116,18 @@ The library uses the following mapping from JSON values types to BJData types ac
    ```

    Likewise, when a JSON object in the above form is serialized using
-    [`to_bjdata`](../../api/basic_json/to_bjdata.md), it is automatically converted into a compact BJData ND-array.
+    [`to_bjdata`](../../api/basic_json/to_bjdata.md), it is automatically converted into a compact BJData ND-array. When
+    the 1-dimensional vector stored in `"_ArraySize_"` contains a single integer or two integers with one being 1, a
+    regular 1-D optimized array is generated instead.

-    When parsing, an ND-array whose dimension vector is empty, contains a single integer, contains two integers with the
-    first being 1, or contains a 0 is returned as a regular (possibly empty) array rather than an annotated object.
-
-    An object is only converted if the annotation describes a packed array that is parsed back into the same annotated
-    object; otherwise it is serialized as a regular JSON object, so the annotation is never lost in a round trip. This requires
-    all of the following:
+    An object is only converted if the annotation actually describes a packed array; otherwise it is serialized as a
+    regular JSON object. This requires all of the following:

    - `"_ArrayType_"` is one of `uint8`, `int8`, `uint16`, `int16`, `uint32`, `int32`, `uint64`, `int64`, `single`,
      `double`, `char`, or `byte`,
    - `"_ArraySize_"` is an array, since the dimensions are written as the ND-array header's length,
-    - `"_ArraySize_"` has at least two entries and is not a 1×N row vector (first entry 1), since other shapes are
-      parsed back as a regular array,
-    - every entry of `"_ArraySize_"` is a positive integer, and their product is representable as a `std::size_t`,
-    - `"_ArrayData_"` is an array holding exactly that many elements, and
+    - every entry of `"_ArraySize_"` is a non-negative integer, and their product is representable as a `std::size_t`,
+    - `"_ArrayData_"` holds exactly that many elements, and
    - every element of `"_ArrayData_"` is a number of the kind named by `"_ArrayType_"` (a floating-point number for
      `single` and `double`, an integer otherwise).

@@ -208,16 +204,6 @@ The library maps BJData types to JSON value types as follows:

    The mapping is **complete** in the sense that any BJData value can be converted to a JSON value.

-!!! info "Round trips"
-
-    A value returned by [`from_bjdata`](../../api/basic_json/from_bjdata.md) can be serialized with
-    [`to_bjdata`](../../api/basic_json/to_bjdata.md) using any combination of options and parsed back into an equal
-    value, and serializing that value again with the same options produces the same bytes. The exception is binary
-    values: they are only written as an optimized binary array (`[$B`) if Draft 3 is enabled and both `use_size` and
-    `use_type` are set. Otherwise, they are written as arrays of integers and parsed back as such (see the notes on
-    binary values above), and serializing such an array again may choose different, but equally valid, type markers.
-    The bytes can then differ, but parsing them again yields the same value.
-
 ??? example

    ```cpp
@@ -109,6 +109,15 @@ The library maps BSON record types to JSON value types as follows:
    If BSON input must be validated for strict specification compliance, validate it separately before passing it to
    `from_bson()`.

+!!! warning "UTF-8 validation of string values"
+
+    The BSON specification requires `string` values (type `0x02`) to be valid UTF-8. This library validates the
+    bytes of every such string at decode time and rejects ill-formed UTF-8 with a
+    [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with `allow_exceptions`
+    set to `false`, a discarded value), rather than only failing later when the resulting value is dumped. Element
+    (key) names and `binary` values (type `0x05`) are unaffected and are never validated, since they are read
+    byte-by-byte as a C string, or are not required to hold text, respectively.
+
 ??? example

    ```cpp
@@ -176,6 +176,16 @@ The library maps CBOR types to JSON value types as follows:

    CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps with keys other than UTF-8 strings are rejected.

+!!! warning "UTF-8 validation of text strings"
+
+    [RFC 8949, Section 3.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-3.1) requires CBOR text strings
+    (major type 3) to be valid UTF-8. This library validates the bytes of every text string (object keys included) at
+    decode time and rejects ill-formed UTF-8 with a
+    [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with
+    `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting value is
+    dumped. Byte strings (major type 2) are unaffected and are never validated, since they are not required to hold
+    text.
+
 !!! warning "Tagged items"

    Tagged items (0xC0..0xDB) will throw a parse error by default. They can be ignored by passing `cbor_tag_handler_t::ignore` to function `from_cbor`, in which case the tag is skipped and the enclosed data item is parsed on its own. They can be stored by passing `cbor_tag_handler_t::store` to function `from_cbor`. Note that no tag is ever interpreted: for instance, a text string tagged with tag 0 (date/time) stays a string.
@@ -136,6 +136,14 @@ The library maps MessagePack types to JSON value types as follows:

    Any MessagePack output created by `to_msgpack` can be successfully parsed by `from_msgpack`.

+!!! warning "UTF-8 validation of string values"
+
+    The MessagePack specification requires `str` values (`fixstr`, `str 8`, `str 16`, `str 32`) to be valid UTF-8.
+    This library validates the bytes of every such string (object keys included) at decode time and rejects
+    ill-formed UTF-8 with a [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or,
+    with `allow_exceptions` set to `false`, a discarded value), rather than only failing later when the resulting
+    value is dumped. `bin`/`ext`/`fixext` values are unaffected and are never validated, since they are not required
+    to hold text.

 ??? example

@@ -91,23 +91,6 @@ security reasons (e.g., Intel Software Guard Extensions (SGX)).

 See [full documentation of `JSON_NO_IO`](../api/macros/json_no_io.md).

-## `JSON_NO_THREAD_LOCAL`
-
-When defined, the library does not use `#!cpp thread_local` storage. Copying a value and comparing two values then
-always avoid the call stack rather than descending into a bounded number of levels first, which is slower but yields the
-same values and the same comparisons.
-
-See [full documentation of `JSON_NO_THREAD_LOCAL`](../api/macros/json_no_thread_local.md).
-
-## `JSON_PRECISE_STREAM_POSITION`
-
-When defined to `1`, [`operator>>`](../api/operator_gtgt.md) and non-strict
-[`sax_parse`](../api/basic_json/sax_parse.md) leave an input stream positioned right after the parsed value, instead of
-also consuming the character that terminates a number. The default value is `0`, which preserves the existing behavior;
-this is planned to become the default in version 4.0.0.
-
-See [full documentation of `JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md).
-
 ## `JSON_SKIP_LIBRARY_VERSION_CHECK`

 When defined, the library will not create a compiler warning when a different version of the library was already
@@ -122,19 +105,6 @@ using the library with compilers that do not fully support C++11 and may only wo

 See [full documentation of `JSON_SKIP_UNSUPPORTED_COMPILER_CHECK`](../api/macros/json_skip_unsupported_compiler_check.md).

-## `JSON_STRICT_NUL_HANDLING`
-
-When defined to `1`, a `'\0'` (NUL) byte anywhere in the input is rejected with `parse_error.101`, like any other
-unexpected byte, instead of being silently treated as end of input (see the
-[FAQ entry](../home/faq.md#nul-bytes-in-the-input) for background). The default value is `0`, which preserves the
-existing behavior; this is planned to become the default in version 4.0.0.
-
-The strict handling can also be enabled with the CMake option
-[`JSON_StrictNulHandling`](../integration/cmake.md#json_strictnulhandling) (`OFF` by default) which sets
-`JSON_STRICT_NUL_HANDLING` accordingly.
-
-See [full documentation of `JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md).
-
 ## `JSON_THROW_USER(exception)`

 This macro overrides `#!cpp throw` calls inside the library. The argument is the exception to be thrown.
@@ -15,10 +15,6 @@ The complete default namespace name is derived as follows:
    - [`JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md) defined non-zero appends `_diag`.
    - [`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](../api/macros/json_use_legacy_discarded_value_comparison.md)
      defined non-zero appends `_ldvcmp`.
-    - [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md) defined non-zero appends `_dp`.
-    - [`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md) defined non-zero appends
-      `_bics`.
-    - [`JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md) defined non-zero appends `_psp`.
 - The inline namespace ends with the suffix `_v` followed by the 3 components of the version number separated by
  underscores. To omit the version component, see [Disabling the version component](#disabling-the-version-component)
  below.
@@ -51,11 +51,7 @@ If you do want to preserve the **insertion order**, you can use the type [`nlohm
    --8<-- "examples/ordered_json.output"
    ```

-Alternatively, [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map) also preserves the insertion order and, unlike [`ordered_map`](../api/ordered_map.md), keeps a lookup index, so it does not have the quadratic cost described below. It is used through a small adapter ([integration](https://github.com/nlohmann/json/issues/485#issuecomment-333652309)).
-
-If the order does not matter and you only want faster lookup, `boost::unordered_flat_map`, `absl::flat_hash_map`, `absl::node_hash_map`, and several other hash maps work through an adapter that restores the template argument order `basic_json` expects; see [Template Parameter Requirements](types/template_parameters.md#objecttype). Note these are *unordered*, not insertion-ordered.
-
-[`tsl::ordered_map`](https://github.com/Tessil/ordered-map) cannot be used: its iterators expose the mapped value as `const`, while `basic_json` needs to modify it in place.
+Alternatively, you can use a more sophisticated ordered map like [`tsl::ordered_map`](https://github.com/Tessil/ordered-map) ([integration](https://github.com/nlohmann/json/issues/546#issuecomment-304447518)) or [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map) ([integration](https://github.com/nlohmann/json/issues/485#issuecomment-333652309)).

 The [`ordered_map`](../api/ordered_map.md) behind `nlohmann::ordered_json` is deliberately minimal and has no lookup
 index, so every key access is a linear scan and building an object of `n` keys costs O(n²). This is unnoticeable at
@@ -41,8 +41,7 @@ document followed by trailing bytes" is accepted rather than rejected. If you ar
 reject any input that is not exactly one JSON document, prefer `parse`.

 When using `operator>>` to read several concatenated values this way, a value that is a number must be followed by
-whitespace, because `operator>>` consumes the character that terminates a number, unless
-[`JSON_PRECISE_STREAM_POSITION`](../../api/macros/json_precise_stream_position.md) is defined to `1` — see the
+whitespace, because `operator>>` consumes the character that terminates a number — see the
 [`operator>>` notes](../../api/operator_gtgt.md#notes) for details and examples.

 ## SAX vs. DOM parsing
@@ -79,8 +79,7 @@ template<
    class NumberFloatType = double,
    template<typename U> class AllocatorType = std::allocator,
    template<typename T, typename SFINAE = void> class JSONSerializer = adl_serializer,
-    class BinaryType = std::vector<std::uint8_t>,
-    class CustomBaseClass = void
+    class BinaryType = std::vector<std::uint8_t>
 >
 class basic_json;
 ```
@@ -107,10 +106,6 @@ using number_float_t = NumberFloatType;
 using binary_t = nlohmann::byte_container_with_subtype<BinaryType>;
 ```

-Not every type can be passed for these template arguments: the library uses the resulting types in ways that imply a
-number of requirements, for instance that `StringType` is `char`-based or that `ArrayType` is vector-like. These
-requirements are collected in [Template Parameter Requirements](template_parameters.md).
-

 ## Objects

@@ -1,747 +0,0 @@
-# Template Parameter Requirements
-
-Class [`basic_json`](../../api/basic_json/index.md) is configurable through eleven template parameters. The library
-never formally states what a type passed for one of these parameters has to provide -- the requirements are implied by
-the way the library uses the resulting [`object_t`](../../api/basic_json/object_t.md),
-[`array_t`](../../api/basic_json/array_t.md), [`string_t`](../../api/basic_json/string_t.md), etc. This page collects
-these requirements so they do not have to be discovered by trial and error. Each section lists the concrete types
-that are known to work for that parameter and the ones that do not, checked against Boost 1.83, Abseil 20250127.0,
-Folly, EASTL 3.21, `ankerl::unordered_dense`, `phmap`, `gtl`, `robin_hood`, `tsl::ordered_map`, and Qt 6.
-
-## How to read this page
-
-Requirements are split into two groups:
-
- **Always required** -- needed to instantiate `basic_json` at all, or needed by functions that virtually every program
-  uses (construction, element access, [`dump`](../../api/basic_json/dump.md)).
- **Required for ...** -- only needed when a particular part of the API is instantiated. Member function templates are
-  only instantiated when they are used, so a type may be perfectly usable even though it does not satisfy these
-  requirements, as long as the corresponding functions are never called.
-
-!!! warning "Requirements are not checked"
-
-    Three requirements are checked with a `#!cpp static_assert`: the array iterator category, the width of
-    [`BinaryType`](#binarytype)'s `value_type`, and [`NumberUnsignedType`](#numberintegertype-and-numberunsignedtype)
-    being at least as wide as [`NumberIntegerType`](#numberintegertype-and-numberunsignedtype). The rest are not
-    diagnosed with dedicated error messages, and violating most of them results in a compiler error somewhere inside
-    the library. Four violations are not caught at compile time at all:
-
-    - A [`StringType`](#stringtype) whose `data()` is not null-terminated compiles and silently misparses numbers,
-      because the lexer hands the buffer to `#!cpp std::strtoull`/`#!cpp std::strtoll`/`#!cpp std::strtod`.
-    - A stateful [`AllocatorType`](#allocatortype) compiles and silently ignores its state: allocation, deallocation,
-      and [`get_allocator()`](../../api/basic_json/get_allocator.md) each use a different default-constructed instance.
-    - The two [cross-specialization conversions](#cross-specialization-conversions) below. These abort on an assertion
-      in a normal build, and only fail silently under `#!cpp NDEBUG`.
-
-## Overview
-
-| Template parameter                                                | Default                           | Notable substitutes                                                   |
-|-------------------------------------------------------------------|-----------------------------------|-----------------------------------------------------------------------|
-| [`ObjectType`](#objecttype)                                       | `std::map`                        | [`nlohmann::ordered_map`](../../api/ordered_map.md), Abseil hash maps |
-| [`ArrayType`](#arraytype)                                         | `std::vector`                     | `#!cpp std::deque`                                                    |
-| [`StringType`](#stringtype)                                       | `std::string`                     | `std::string`-like types over `char`                                  |
-| [`BooleanType`](#booleantype)                                     | `bool`                            | none worth using                                                      |
-| [`NumberIntegerType`](#numberintegertype-and-numberunsignedtype)  | `std::int64_t`                    | any signed integer type                                               |
-| [`NumberUnsignedType`](#numberintegertype-and-numberunsignedtype) | `std::uint64_t`                   | any unsigned integer type at least as wide as `NumberIntegerType`     |
-| [`NumberFloatType`](#numberfloattype)                             | `double`                          | `float` (`long double`: no binary formats)                            |
-| [`AllocatorType`](#allocatortype)                                 | `std::allocator`                  | stateless allocators                                                  |
-| [`JSONSerializer`](#jsonserializer)                               | `adl_serializer`                  | serializers with the same interface                                   |
-| [`BinaryType`](#binarytype)                                       | `#!cpp std::vector<std::uint8_t>` | `#!cpp std::vector<char>`                                             |
-| [`CustomBaseClass`](#custombaseclass)                             | `void`                            | any default-constructible class                                       |
-
-!!! warning "Third-party containers and incomplete types"
-
-    `object_t` is instantiated inside the definition of `basic_json` -- it is probed for a `key_compare` member to
-    form [`object_comparator_t`](../../api/basic_json/object_comparator_t.md) -- i.e. while `basic_json` is still an
-    incomplete type. `#!cpp std::map` is required by the standard to support incomplete mapped types; most
-    third-party maps are not, and inspecting the mapped type at class scope (for instance with
-    `#!cpp std::is_trivially_move_assignable`) makes them unusable as `ObjectType`, no matter how their template
-    arguments are adapted. This rules out `absl::btree_map`, `phmap::btree_map`, `gtl::btree_map`,
-    `robin_hood::unordered_node_map`, `folly::F14FastMap`, and `eastl::hash_map`.
-
-    `array_t` is only *named* in the class definition and is not instantiated until `basic_json` is complete, so an
-    `ArrayType` that inspects its value type at class scope is generally fine -- `boost::container::small_vector` and
-    `static_vector` both reject incomplete value types yet work here. `absl::InlinedVector` is the exception: the
-    `#!cpp std::is_trivially_move_assignable<basic_json>` it evaluates while instantiating itself re-enters the
-    library's own trait machinery mid-instantiation.
-
-!!! note "Folly requires C++20"
-
-    Folly's headers use `#!cpp consteval` and `#!cpp std::type_identity`, so any `basic_json` specialization that
-    names a Folly type has to be compiled as C++20 or later, whatever the rest of the library supports.
-
-## `ObjectType`
-
-`ObjectType` is instantiated as
-
-```cpp
-using object_t = ObjectType<StringType,                                    // key_type
-                            basic_json,                                    // mapped_type
-                            default_object_comparator_t,                   // key_compare
-                            AllocatorType<std::pair<const StringType,
-                                                    basic_json>>>;         // allocator_type
-```
-
-i.e., the template arguments follow the order and meaning of `std::map`.
-
-### Always required
-
- The template must be usable with **four** type arguments in the order shown above. The third argument is a
-  **comparator**; containers that expect something else in this position (e.g., a hash function) need an alias template
-  or wrapper -- see [Notes](#notes).
- An optional member type `key_compare`. If it is present it becomes
-  [`object_comparator_t`](../../api/basic_json/object_comparator_t.md); otherwise
-  [`default_object_comparator_t`](../../api/basic_json/default_object_comparator_t.md) is used.
- Member types `key_type`, `mapped_type`, `value_type`, and `iterator`.
- `value_type` must behave like `#!cpp std::pair<const key_type, mapped_type>`; the library accesses `.first` and
-  `.second` on it.
- `iterator` must be default-constructible and satisfy
-  [LegacyBidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator). The type returned
-  by `cbegin()`/`cend()` must satisfy the same requirements.
- Constructors: default, copy, move, and from an iterator range `(first, last)`.
- Member functions `begin()`, `end()`, `cbegin()`, `cend()`, `empty()`, `size()`, `max_size()`, `clear()`,
-  `find(key)`, `count(key)`, `emplace(key, value)`, `insert(value_type)`, `insert(first, last)`, `operator[](key)`,
-  `erase(iterator)`, and `erase(first, last)`. `erase(iterator)` may return the following iterator or `#!cpp void`;
-  in the latter case the library computes the successor itself, before erasing.
- `erase(key)` is **optional**: if the container does not provide one, the library falls back to `find(key)` followed
-  by `erase(iterator)`.
- `at(key)` is required only by [`to_ubjson`](../../api/basic_json/to_ubjson.md) and
-  [`to_bjdata`](../../api/basic_json/to_bjdata.md), but every container tried here provides it.
- `emplace` and `insert(value_type)` must return `#!cpp std::pair<iterator, bool>` and must have **unique-key**
-  semantics; multimaps cannot be used.
- The type must be swappable (via `std::swap` or an ADL `swap`).
- The comparison operators `==` and `<`; `!=`, `<=`, `>`, and `>=` are derived from them. Where the library uses
-  three-way comparison (C++20), `==` and `<=>` are required **instead** -- the six two-way operators do not satisfy
-  it. They implement [`basic_json`'s comparison operators](../../api/basic_json/operator_eq.md).
-
-### Required for heterogeneous key lookup
-
-The overloads of [`at`](../../api/basic_json/at.md), [`operator[]`](../../api/basic_json/operator%5B%5D.md),
-[`find`](../../api/basic_json/find.md), [`contains`](../../api/basic_json/contains.md),
-[`count`](../../api/basic_json/count.md), [`erase`](../../api/basic_json/erase.md), and
-[`value`](../../api/basic_json/value.md) that accept a key type other than `object_t::key_type` require
-
- a **transparent** comparator, i.e. [`object_comparator_t`](../../api/basic_json/object_comparator_t.md) has a member
-  type `is_transparent` (this is why the default comparator is `#!cpp std::less<>` since C++14), and
- corresponding heterogeneous `find`, `count`, `erase`, and `operator[]` overloads on the container.
-
-### Notes
-
-#### `std::unordered_map` needs an adapter
-
-`#!cpp std::unordered_map` cannot be passed directly: its third template parameter is a hash function, but
-`basic_json` passes a comparator in that position. An alias template or wrapper that restores the expected argument
-order makes it usable:
-
-```cpp
-template<class Key, class T, class IgnoredCompare, class Allocator>
-struct unordered_map_object
-    : std::unordered_map<Key, T, std::hash<Key>, std::equal_to<Key>, Allocator>
-{
-    using base_t = std::unordered_map<Key, T, std::hash<Key>, std::equal_to<Key>, Allocator>;
-    using base_t::base_t;
-};
-
-using unordered_json = nlohmann::basic_json<unordered_map_object>;
-```
-
-Whether `#!cpp std::unordered_map` can be instantiated at all depends on the standard library: `object_t` is formed
-while `basic_json` is still incomplete (see the warning above), and libstdc++ 9 needs the size of the mapped type to
-instantiate the hash map's node type, so the adapter does not compile there. Newer libstdc++ versions, and the hash
-maps listed below, do not have that problem.
-
-The adapter above works verbatim for Abseil's, Boost's, `phmap`'s and `gtl`'s hash maps, which all place the hash
-function third and take a `#!cpp std::pair<const Key, T>` allocator fifth. Two need a different adapter:
-
- `ankerl::unordered_dense` expects an allocator over `#!cpp std::pair<Key, T>` (non-const key), so the allocator has
-  to be rebound to that or dropped.
- `robin_hood`'s fifth parameter is the non-type `MaxLoadFactor100`, so its adapter must drop the allocator entirely.
-
-None of these hash maps defines `key_compare`, so all of them additionally rely on `object_comparator_t` falling back
-to [`default_object_comparator_t`](../../api/basic_json/default_object_comparator_t.md); see
-[`object_comparator_t`](../../api/basic_json/object_comparator_t.md).
-
-#### Abseil hash maps
-
-`absl::flat_hash_map` and `absl::node_hash_map` tolerate an incomplete value type, but they take a hash function as
-their third template argument. The same adapter as for `#!cpp std::unordered_map` makes them usable:
-
-```cpp
-template<class Key, class T, class IgnoredCompare, class Allocator>
-struct flat_hash_object
-    : absl::flat_hash_map<Key, T, absl::Hash<Key>, std::equal_to<Key>, Allocator>
-{
-    using base_t = absl::flat_hash_map<Key, T, absl::Hash<Key>, std::equal_to<Key>, Allocator>;
-    using base_t::base_t;
-};
-
-using flat_hash_json = nlohmann::basic_json<flat_hash_object>;
-```
-
-`absl::node_hash_map` keeps references to the mapped values valid across insertions; `absl::flat_hash_map` does not,
-which makes it behave like [`ordered_json`](../../api/ordered_json.md) with respect to
-[iterator invalidation](../../api/basic_json/index.md#iterator-invalidation). Both expose a `capacity()` member
-function, so [`JSON_DIAGNOSTICS`](../../api/macros/json_diagnostics.md) treats them conservatively and keeps the
-parent pointers correct either way.
-
-#### Iteration order
-
-The library never relies on the container's iteration order for correctness; it does determine the order in which
-object keys are serialized by [`dump`](../../api/basic_json/dump.md) and visited by
-[`items`](../../api/basic_json/items.md). See [Object Order](../object_order.md).
-
-#### `capacity()` marks a container as insertion-ordered
-
-With [`JSON_DIAGNOSTICS`](../../api/macros/json_diagnostics.md) enabled, the library detects insertion-ordered maps by
-probing for a `capacity()` member function (`nlohmann::ordered_map` inherits it from `std::vector`) and refreshes all
-parent pointers after every insertion. An `ObjectType` that happens to have a `capacity()` member is therefore treated
-conservatively -- this is correct, but slower.
-
-#### Key order and duplicate keys
-
-The library does not sort or de-duplicate keys itself; the behavior described in
-[`object_t`](../../api/basic_json/object_t.md) is entirely the behavior of the chosen container.
-
-!!! tip "Reference implementation"
-
-    `docs/mkdocs/docs/examples/custom_object_type.hpp` wraps a private `#!cpp std::map` and satisfies every
-    requirement above. It does not define `key_compare`, so `object_comparator_t` falls back to
-    [`default_object_comparator_t`](../../api/basic_json/default_object_comparator_t.md) -- a good starting point for
-    a custom `ObjectType`.
-
-    ```cpp
-    --8<-- "examples/custom_object_type.hpp"
-    ```
-
-??? example "Compiling and using it"
-
-    ```cpp
-    --8<-- "examples/custom_object_type.cpp"
-    ```
-
-    Output:
-
-    ```json
-    --8<-- "examples/custom_object_type.output"
-    ```
-
-### Compatible containers
-
-| Container                                                                        | Notes                                                                         |
-|----------------------------------------------------------------------------------|-------------------------------------------------------------------------------|
-| `#!cpp std::map` (default)                                                       |                                                                               |
-| [`nlohmann::ordered_map`](../../api/ordered_map.md)                              | used by [`ordered_json`](../../api/ordered_json.md); keeps insertion order    |
-| [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map)                     | keeps insertion order; adapter puts `fifo_map_compare` in the comparator slot |
-| `boost::container::map`, `boost::container::flat_map`                            | no adapter needed                                                             |
-| `#!cpp std::unordered_map`                                                       | through the adapter above; not with libstdc++ 9, see the note                 |
-| `boost::unordered_map`, `boost::unordered_flat_map`, `boost::unordered_node_map` | through the adapter above                                                     |
-| `absl::flat_hash_map`, `absl::node_hash_map`                                     | through the adapter above; `flat_hash_map` moves mapped values on rehash      |
-| `phmap::flat_hash_map`, `phmap::node_hash_map`, `gtl::flat_hash_map`             | through the adapter above                                                     |
-| `ankerl::unordered_dense::map` and `segmented_map`                               | adapter must rebind or drop the allocator                                     |
-| `robin_hood::unordered_flat_map`                                                 | adapter must drop the allocator                                               |
-| `folly::F14NodeMap`                                                              | through the adapter above; requires C++20, see the note above                 |
-| `folly::sorted_vector_map`                                                       | alias must drop the allocator, whose value type it disagrees on               |
-
-### Containers that cannot be used
-
-| Container                                                                | Reason                                                                                                              |
-|--------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------|
-| `absl::btree_map`, `phmap::btree_map`, `gtl::btree_map`                  | require a complete mapped type                                                                                      |
-| `robin_hood::unordered_node_map`, `folly::F14FastMap`, `eastl::hash_map` | require a complete mapped type                                                                                      |
-| `eastl::map`                                                             | EASTL iterators do not work with `#!cpp std::iterator_traits`                                                       |
-| `tsl::ordered_map`                                                       | its iterators expose the mapped value as `#!cpp const`                                                              |
-| `QMap`                                                                   | no `value_type` member type                                                                                         |
-| `QHash`                                                                  | its `value_type` is the mapped type rather than a key/value pair, and its iterators dereference to the mapped value |
-| `#!cpp std::multimap`, `#!cpp std::unordered_multimap`                   | `emplace` does not return `#!cpp std::pair<iterator, bool>`                                                         |
-
-## `ArrayType`
-
-`ArrayType` is instantiated as
-
-```cpp
-using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
-```
-
-### Always required
-
- The template must be usable with **two** type arguments (value type and allocator).
- Member types `value_type` and `iterator`.
- Constructors: default, copy, and move; and from an iterator range `(first, last)`.
- Member functions `begin()`, `end()`, `cbegin()`, `cend()`, `empty()`, `size()`, `max_size()`, `clear()`,
-  `operator[](size_type)`, `back()`, `push_back()`, `emplace_back()`, `pop_back()`, `resize()`,
-  `insert()` (single element, count, and range), `erase(pos)`, and `erase(first, last)`.
-  `basic_json::insert(pos, initializer_list)` goes through the range overload, so no initializer-list `insert` is
-  needed. `at(size_type)` is **not** required: [`basic_json::at(size_type)`](../../api/basic_json/at.md) checks the
-  index itself and then uses `operator[]`.
- `iterator` must be default-constructible, and it as well as the type returned by `cbegin()`/`cend()` must satisfy
-  [LegacyRandomAccessIterator](https://en.cppreference.com/w/cpp/named_req/RandomAccessIterator).
-  A `#!cpp static_assert` only checks for
-  [LegacyBidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator), but
-  [`dump`](../../api/basic_json/dump.md) (`cend() - 1`),
-  [`erase(idx)`](../../api/basic_json/erase.md) (`begin() + idx`), and the random-access operations of
-  [`basic_json::iterator`](../../api/basic_json/begin.md) require random access.
- The comparison operators, as for [`ObjectType`](#objecttype): `==` and `<`, or `==` and `<=>` under C++20.
-
-### Required for individual functions
-
- A member type `value_type`, for [`to_bson`](../../api/basic_json/to_bson.md) of an array.
- A constructor from `(count, value)`, for
-  [`basic_json(size_type, const basic_json&)`](../../api/basic_json/basic_json.md).
- Swappability, via `#!cpp std::swap` or an ADL `swap`, for [`swap(array_t&)`](../../api/basic_json/swap.md).
-
-!!! note "`capacity()` is optional"
-
-    With [`JSON_DIAGNOSTICS`](../../api/macros/json_diagnostics.md) enabled, the library reads `array_t::capacity()`
-    to find out whether adding an element reallocated the array and moved its elements, which would invalidate the
-    parent pointers. An array type without a `capacity()` member function is handled conservatively: the parent
-    pointers of all elements are refreshed after every insertion, which makes adding *n* elements cost O(*n*²). Only
-    diagnostics builds pay this; without them `capacity()` is never called.
-
-!!! tip "Reference implementation"
-
-    `docs/mkdocs/docs/examples/custom_array_type.hpp` wraps a private `#!cpp std::vector` and satisfies every
-    requirement above -- a good starting point for a custom `ArrayType`.
-
-    ```cpp
-    --8<-- "examples/custom_array_type.hpp"
-    ```
-
-??? example "Compiling and using it"
-
-    ```cpp
-    --8<-- "examples/custom_array_type.cpp"
-    ```
-
-    Output:
-
-    ```json
-    --8<-- "examples/custom_array_type.output"
-    ```
-
-### Compatible containers
-
-| Container                                               | Notes                                                                                     |
-|---------------------------------------------------------|-------------------------------------------------------------------------------------------|
-| `#!cpp std::vector` (default)                           |                                                                                           |
-| `#!cpp std::deque`                                      | references survive appends, but not insertions elsewhere; see the `capacity()` note above |
-| `#!cpp std::pmr::vector`                                | through an alias, as the allocator comes from `AllocatorType` instead                     |
-| `boost::container::vector`, `deque`, `devector`         |                                                                                           |
-| `boost::container::stable_vector`                       | the only one tried that keeps references valid across *every* insertion                   |
-| `boost::container::small_vector`, `folly::small_vector` | through an alias that fixes the inline capacity                                           |
-| `boost::container::static_vector`                       | through the same kind of alias, for arrays that stay within the fixed capacity            |
-| `folly::fbvector`                                       | requires C++20, see the note above                                                        |
-
-### Containers that cannot be used
-
-| Container                           | Reason                                                                                        |
-|-------------------------------------|-----------------------------------------------------------------------------------------------|
-| `#!cpp std::list`                   | no `operator[]`, and no random-access iterators                                               |
-| `eastl::vector`, `QList`, `QVector` | no `max_size()`; they handle the incomplete value type fine                                   |
-| `absl::InlinedVector`               | requires a complete value type, see the note above                                            |
-| `absl::FixedArray`                  | the size is fixed at construction, so `resize`, `push_back`, `insert` and `erase` are missing |
-
-## `StringType`
-
-`StringType` is used **both** for JSON string values and for the keys of JSON objects
-(`string_t` and `object_t::key_type`).
-
-### Always required
-
- A member type `value_type` that is one byte wide and `char`-compatible. The library stores and processes UTF-8
-  encoded `char` data and hands `data()` to `#!cpp std::strtoull`/`#!cpp std::strtoll`.
-  `#!cpp std::wstring`, `#!cpp std::u16string`, and `#!cpp std::u32string` are **not** valid choices; see the FAQ on
-  [wide string handling](../../home/faq.md#wide-string-handling).
- Constructors: default, copy, move, from `#!cpp const char*` (which must not be `#!cpp explicit`), from
-  `#!cpp (const char*, size_type)`, and from `#!cpp (size_type, char)`; and copy or move assignment.
- Member functions `size()`, `clear()`, `resize(n, c)`, `data()`, `push_back(char)`, and `operator[]`
-  (const and non-const, returning references). `c_str()` and `back()` are **not** required.
- `data()` must return a pointer to a contiguous, **null-terminated** buffer -- the parser hands it to
-  `#!cpp std::strtoull`. A type whose `data()` is not null-terminated does not fail to compile; it silently
-  misparses numbers.
- `append(const char*, size_type)`, used by [`dump`](../../api/basic_json/dump.md), and `append(const StringType&)`,
-  used by the CBOR reader for indefinite-length strings. The library's internal string concatenation additionally has
-  to append a `#!cpp char` and a `#!cpp const char*`; for each it selects between `append(arg)`, `#!cpp operator+=`,
-  `append(first, last)`, and `append(data, size)`.
- The comparison operator `==` against another `StringType`, and `<` for use as a key of the chosen
-  [`ObjectType`](#objecttype) (with the default comparator, `#!cpp std::less<>` must be able to compare two
-  `StringType` values, and a `StringType` with the key types used for lookup). `!=` is never applied to a
-  `StringType`, and `==` against `#!cpp const char*` is resolved by the implicit `#!cpp const char*` constructor.
-
-### Required for the binary formats
-
- `resize(n)`, used by the readers to make room for a block of bytes.
- Non-const `operator[]`, into which the readers `#!cpp std::memcpy` those bytes. A non-`#!cpp const` `data()` would
-  serve just as well, but `#!cpp std::string` has only had one since C++17, and the library still supports C++11.
-
-### Required for JSON Pointer, `flatten`, and `diff`
-
- A static member `npos` and the member function `find_first_of(char, size_type)` -- together with `data()`,
-  `reserve(n)`, and `append(const char*, size_type)` they implement the escaping and unescaping of reference tokens
-  described in RFC 6901. Neither `find(const StringType&, size_type)`, nor `substr(pos, count)`, nor
-  `replace(pos, count, const StringType&)` is required.
- `empty()`.
- `begin()` and `end()` -- used by
-  [`operator[](const json_pointer&)`](../../api/basic_json/operator%5B%5D.md) to decide whether a reference token
-  denotes an array index.
-
-### Required for other functionality
-
-| Functionality                                                                                                                     | Additional requirement                                                                                                                                                                       |
-|-----------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| [`diff`](../../api/basic_json/diff.md), [`items`](../../api/basic_json/items.md), [`std::hash`](../../api/basic_json/std_hash.md) | conversion of a `#!cpp std::size_t` to `StringType`: either assignability from the result of `#!cpp std::to_string`, or an ADL overload `#!cpp void int_to_string(StringType&, std::size_t)` |
-| [`std::hash<basic_json>`](../../api/basic_json/std_hash.md)                                                                       | additionally a specialization of `#!cpp std::hash<StringType>`                                                                                                                               |
-| [`to_bson`](../../api/basic_json/to_bson.md)                                                                                      | `find(value_type)` and `npos`                                                                                                                                                                |
-| [`parse`](../../api/basic_json/parse.md) from a `string_t`                                                                        | the input adapters must accept it; otherwise pass a character range                                                                                                                          |
-| `#!cpp operator<<(std::ostream&, const json_pointer&)`                                                                            | streamability to `#!cpp std::ostream`                                                                                                                                                        |
-| exception messages                                                                                                                | `data()` and `size()`, or `begin()` and `end()`                                                                                                                                              |
-
-### Compatible types
-
-| Type                                                            | Notes                                                                                                                                                                                                                                         |
-|-----------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| `#!cpp std::string` (default)                                   |                                                                                                                                                                                                                                               |
-| `#!cpp std::basic_string` with a custom **stateless** allocator |                                                                                                                                                                                                                                               |
-| `#!cpp std::pmr::string`                                        | see the warning below before relying on the memory resource                                                                                                                                                                                   |
-| `boost::container::string`                                      | needs a user-supplied `#!cpp std::hash` specialization (Boost provides `boost::hash` instead)                                                                                                                                                 |
-| `folly::fbstring`                                               | requires C++20, see the note above                                                                                                                                                                                                            |
-| `eastl::string`                                                 | needs a user-supplied `#!cpp std::hash` and an ADL `int_to_string` (it is not assignable from a `#!cpp std::string`); [`parse`](../../api/basic_json/parse.md) does not accept it directly -- pass a character range or a `#!cpp std::string` |
-| a custom string class in a user-defined namespace               | if the requirements above are met                                                                                                                                                                                                             |
-
-### Types that cannot be used
-
-| Type                                                                 | Reason                                                                                                  |
-|----------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------|
-| `#!cpp std::wstring`, `#!cpp std::u16string`, `#!cpp std::u32string` | the character type is not one byte wide                                                                 |
-| `#!cpp std::u8string`                                                | one byte wide, but `#!cpp char8_t` is not `#!cpp char`-compatible                                       |
-| `absl::Cord`                                                         | no `value_type`, and the storage is not contiguous                                                      |
-| `QString`                                                            | no `append(const char*, size_type)`; its `QChar` is also two bytes wide, though that is never diagnosed |
-
-!!! warning "A `std::pmr::string` mostly does not use the memory resource you choose"
-
-    `basic_json` cannot be given an allocator or a memory resource. `AllocatorType` is default-constructed at every
-    allocation and has to be stateless (see [`AllocatorType`](#allocatortype)), and string values the library creates
-    are constructed with their own default allocator. So:
-
-    - Every string the library itself produces -- from [`parse`](../../api/basic_json/parse.md), from
-      [`dump`](../../api/basic_json/dump.md), or by default construction -- allocates from
-      `#!cpp std::pmr::get_default_resource()`.
-    - **Copying** an arena-backed string into a value silently drops its memory resource: the copy lands on the
-      default resource, because `#!cpp std::pmr::polymorphic_allocator` does not propagate on copy construction.
-      Nothing warns about this.
-    - **Moving** one in does keep it, and later growth still allocates from that arena -- but it does not survive a
-      copy of the enclosing `basic_json`.
-    - Passing `#!cpp std::pmr::polymorphic_allocator` as `AllocatorType` does not work around any of this; it does
-      not compile.
-
-    Apart from moving a string in, the only way to redirect these allocations is the process-global
-    `#!cpp std::pmr::set_default_resource()`.
-
-!!! tip "Reference implementation"
-
-    `docs/mkdocs/docs/examples/custom_string_type.hpp` wraps a private `#!cpp std::string` and satisfies every
-    requirement above -- a good starting point for a custom `StringType`. The unit test
-    `tests/src/unit-alt-string.cpp` contains a more thorough variant, `alt_string`, exercised against a larger part
-    of the API.
-
-    ```cpp
-    --8<-- "examples/custom_string_type.hpp"
-    ```
-
-??? example "Compiling and using it"
-
-    ```cpp
-    --8<-- "examples/custom_string_type.cpp"
-    ```
-
-    Output:
-
-    ```json
-    --8<-- "examples/custom_string_type.output"
-    ```
-
-## `BooleanType`
-
-`boolean_t` is stored **directly** inside `basic_json`, as a member of an anonymous union.
-
-### Always required
-
- A literal type that is trivially default-constructible, trivially copyable, and trivially destructible; otherwise the
-  union's special member functions are deleted.
- **Implicitly** convertible from `#!cpp bool` -- an `#!cpp explicit` constructor is not enough, because the
-  `to_json` overload for a custom `BooleanType` is constrained on `#!cpp std::is_convertible` -- and contextually
-  convertible to `#!cpp bool` (here an `#!cpp explicit operator bool` is fine).
- Comparison operators `==`, `!=`, `<`, `<=`, `>`, `>=` (or `<=>`).
- Convertible from and to `#!cpp bool` through the serializer, because
-  [`get<bool>()`](../../api/basic_json/get.md) is used internally.
-
-There is little reason to use anything other than `#!cpp bool` here.
-
-### Compatible types
-
-`#!cpp bool` is the only usable choice. Another trivially copyable type that is implicitly convertible to and from
-`#!cpp bool` -- `#!cpp std::uint8_t`, say -- does compile, and JSON booleans still round-trip, but the type then
-serves as both `boolean_t` and an ordinary integer: `basic_json` can no longer be constructed or assigned from a
-`#!cpp std::uint8_t` at all (the boolean and unsigned-integer `to_json` overloads become ambiguous), and
-[`get<std::uint8_t>()`](../../api/basic_json/get.md) on a number throws
-[`type_error.302`](../../home/exceptions.md#jsonexceptiontype_error302) instead of returning the value.
-
-## `NumberIntegerType` and `NumberUnsignedType`
-
-Both types are stored **directly** inside `basic_json`'s union.
-
-### Always required
-
- `#!cpp std::is_integral` must be satisfied: `NumberIntegerType` must be a **signed** integer type,
-  `NumberUnsignedType` an **unsigned** integer type. Class types are not supported -- among others, the constructors
-  taking integer values are constrained on `#!cpp std::is_integral`.
- Trivially default-constructible, trivially copyable, and trivially destructible (union member).
- `#!cpp std::numeric_limits` must be specialized for both types.
- `NumberUnsignedType` must be able to represent the absolute value of every `NumberIntegerType` value; serialization
-  of negative numbers converts the value to `NumberUnsignedType`. A `#!cpp static_assert` requires it to be at least as
-  wide as `NumberIntegerType`, which is what that amounts to for the standard integer types.
- Both types must fit into the internal 64-character number buffer used by
-  [`dump`](../../api/basic_json/dump.md), which is the case for all standard integer types.
- [`std::hash<basic_json>`](../../api/basic_json/std_hash.md) additionally requires `#!cpp std::hash` specializations.
-
-### Notes
-
-The number types influence what the parser accepts: an integer literal that does not round-trip through the chosen type
-is stored as [`number_float_t`](../../api/basic_json/number_float_t.md) instead. Choosing types narrower than 64 bits
-therefore silently changes parse results rather than raising an error. See
-[Number Handling](number_handling.md) for details.
-
-### Compatible types
-
-| Type pair                                                                                    | Support                                                                                                                                                                                          |
-|----------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| `#!cpp std::int64_t` / `#!cpp std::uint64_t` (default)                                       | full                                                                                                                                                                                             |
-| `#!cpp std::int32_t` / `#!cpp std::uint32_t`, `#!cpp long long` / `#!cpp unsigned long long` | full; narrower types change which literals the parser can represent                                                                                                                              |
-| any other pair of standard signed/unsigned integer types                                     | full                                                                                                                                                                                             |
-| class types, enumerations                                                                    | not usable; `#!cpp std::is_integral` must hold                                                                                                                                                   |
-| `#!cpp bool`, or a type already used for another member of the union                         | not usable; `#!cpp std::is_integral<bool>` is in fact `#!cpp true`, but the `get_impl_ptr` overloads for `boolean_t`, `number_integer_t`, `number_unsigned_t` and `number_float_t` would collide |
-
-## `NumberFloatType`
-
-`number_float_t` is stored **directly** inside `basic_json`'s union.
-
-### Always required
-
- Trivially default-constructible, trivially copyable, and trivially destructible (union member).
- `#!cpp std::numeric_limits` must be specialized; `max_digits10` is used to size the conversion.
- `#!cpp std::isfinite` must be applicable to the type.
-
-### Required for parsing and serialization
-
-`NumberFloatType` must be one of `#!cpp float`, `#!cpp double`, or `#!cpp long double`:
-
- The [parser](../parsing/index.md) converts number literals with `#!cpp std::strtof`, `#!cpp std::strtod`, or
-  `#!cpp std::strtold`; the library provides overloads for exactly these three types.
- [`dump`](../../api/basic_json/dump.md) falls back to `#!cpp std::snprintf` with the `%g` and `%Lg` conversion
-  specifiers, for which the library likewise provides only `#!cpp double` and `#!cpp long double` overloads
-  (`#!cpp float` is promoted to `#!cpp double`).
-
-If `#!cpp std::numeric_limits<NumberFloatType>` describes an IEEE 754 binary32 or binary64 number, `dump` uses the
-Grisu2 algorithm, which produces the shortest representation that round-trips. Otherwise the `snprintf` fallback with
-`max_digits10` digits is used.
-
-### Required for the binary formats
-
-`NumberFloatType` must be `#!cpp float` or `#!cpp double`. The writers for
-[CBOR, MessagePack, UBJSON, BJData, and BSON](../binary_formats/index.md) map a floating-point value onto an IEEE 754
-binary32 or binary64 field and have no encoding for `#!cpp long double`.
-
-### Compatible types
-
-| Type                     | Support                                                                                                               |
-|--------------------------|-----------------------------------------------------------------------------------------------------------------------|
-| `#!cpp double` (default) | full; short round-trip output through Grisu2                                                                          |
-| `#!cpp float`            | full; short round-trip output through Grisu2                                                                          |
-| `#!cpp long double`      | `dump` and `parse` only; the binary format writers do not compile, as they only handle IEEE 754 binary32 and binary64 |
-| any other type           | not usable                                                                                                            |
-
-## `AllocatorType`
-
-`AllocatorType` is instantiated with **one** argument, for each of `object_t`, `array_t`, `string_t`, `binary_t`,
-`basic_json`, and `#!cpp std::pair<const StringType, basic_json>`.
-
-### Always required
-
- The template must be usable with exactly one type argument. The library instantiates `AllocatorType<T>` directly and
-  never uses `#!cpp std::allocator_traits<...>::rebind_alloc`.
- It must satisfy the [Allocator](https://en.cppreference.com/w/cpp/named_req/Allocator) named requirement so that
-  `#!cpp std::allocator_traits` can be used with it.
- It must be **default-constructible and stateless**. Objects are allocated with a default-constructed allocator and
-  deallocated with a *different* default-constructed allocator, and
-  [`get_allocator()`](../../api/basic_json/get_allocator.md) returns a default-constructed instance. Allocators
-  carrying state are not supported, so there is no way to tell a `basic_json` where to allocate from; see the note
-  under [`StringType`](#stringtype) for what that means in practice. A stateful allocator is **not diagnosed**: it
-  compiles and silently ignores the state.
- It must support **incomplete types**: `AllocatorType<basic_json>` is instantiated inside the definition of
-  `basic_json` itself.
- `#!cpp std::allocator_traits<AllocatorType<basic_json>>::pointer` becomes
-  [`basic_json::pointer`](../../api/basic_json/index.md#container-types), and iterators are constructed from raw
-  `#!cpp basic_json*` values. The `pointer` type must therefore be a plain pointer; fancy pointers are not supported.
-
-### Compatible types
-
-| Type                                                              | Support                                |
-|-------------------------------------------------------------------|----------------------------------------|
-| `#!cpp std::allocator` (default)                                  | full                                   |
-| a custom stateless allocator template                             | full                                   |
-| stateful allocators, e.g. `#!cpp std::pmr::polymorphic_allocator` | not usable; see the requirements above |
-
-## `JSONSerializer`
-
-`JSONSerializer` is instantiated as `JSONSerializer<T, void>` and defaults to
-[`adl_serializer`](../../api/adl_serializer/index.md).
-
-### Always required
-
- The template must accept **two** type arguments. It does not have to give the second one a default -- `basic_json`
-  declares the parameter as `#!cpp template<typename T, typename SFINAE = void> class JSONSerializer`, so uses such as
-  `#!cpp JSONSerializer<T>` inside the library supply `#!cpp void` themselves. The second parameter exists so that
-  partial specializations can be constrained by SFINAE.
- For every type `T` that is converted **to** a JSON value, a static member function
-  `#!cpp static void to_json(basic_json&, T)` must exist.
- For every type `T` that is converted **from** a JSON value, either
-  `#!cpp static void from_json(const basic_json&, T&)` or `#!cpp static T from_json(const basic_json&)` must exist.
-  The latter form is required for types that are not default-constructible; see
-  [Arbitrary Types Conversions](../arbitrary_types.md).
- To support the [converting constructor](../../api/basic_json/basic_json.md) between different `basic_json`
-  specializations, `to_json` must be available for `boolean_t`, `number_integer_t`, `number_unsigned_t`,
-  `number_float_t`, `string_t`, `object_t`, `array_t`, and `binary_t` of the *source* specialization.
-
-### Compatible types
-
-| Type                                                                      | Support                                                           |
-|---------------------------------------------------------------------------|-------------------------------------------------------------------|
-| [`nlohmann::adl_serializer`](../../api/adl_serializer/index.md) (default) | full                                                              |
-| a class template deriving from `adl_serializer`                           | full; the usual way to change behavior while keeping the defaults |
-| an unrelated template with the same interface                             | full, but it has to handle every type the library converts        |
-
-## `BinaryType`
-
-`BinaryType` is not a JSON type; it is used for the byte strings of the
-[binary formats](../binary_formats/index.md). It is wrapped as
-
-```cpp
-using binary_t = nlohmann::byte_container_with_subtype<BinaryType>;
-```
-
-### Always required
-
- A non-`final` class type -- [`byte_container_with_subtype`](../../api/byte_container_with_subtype/index.md) derives
-  from it publicly.
- A member type `value_type` that is **exactly one byte** wide (e.g., `#!cpp std::uint8_t`, `#!cpp char`, or
-  `#!cpp std::byte`). Readers and writers reinterpret the container's storage as raw bytes, so a wider `value_type` is
-  rejected with a `#!cpp static_assert`.
- Contiguous storage: the binary readers `#!cpp std::memcpy` into `#!cpp &binary[n]`, the writers `reinterpret_cast`
-  `data()`. `#!cpp data() + n` would do for the readers too, but they share one helper with
-  [`StringType`](#stringtype), whose non-`#!cpp const` `data()` is C++17 and later only.
- Default-constructible, copy-constructible, and move-constructible.
- Member functions `size()`, `empty()`, `data()`, `resize()`, `operator[]`, `back()`, `begin()`, `end()`, `cbegin()`,
-  and `cend()` with random-access iterators, and `insert(pos, first, last)`, which the CBOR reader uses to join the
-  chunks of an indefinite-length byte string. `push_back()` is **not** required.
- Comparison operators: `==` is used by
-  [`byte_container_with_subtype`](../../api/byte_container_with_subtype/index.md), the relational operators by
-  [`basic_json`'s comparison operators](../../api/basic_json/operator_le.md).
-
-### Required for individual functions
-
- `clear()`, for [`basic_json::clear()`](../../api/basic_json/clear.md).
-
-`max_size()`, `at()`, `reserve()`, `erase()`, `pop_back()`, and `emplace_back()` are **not** used at all.
-
-See [`binary_t`](../../api/basic_json/binary_t.md) for how a non-default `BinaryType` changes the meaning of assigning
-such a container to a `basic_json` value.
-
-!!! tip "Reference implementation"
-
-    `docs/mkdocs/docs/examples/custom_binary_type.hpp` wraps a private `#!cpp std::vector<std::uint8_t>` and satisfies
-    every requirement above -- a good starting point for a custom `BinaryType`.
-
-    ```cpp
-    --8<-- "examples/custom_binary_type.hpp"
-    ```
-
-??? example "Compiling and using it"
-
-    ```cpp
-    --8<-- "examples/custom_binary_type.cpp"
-    ```
-
-    Output:
-
-    ```json
-    --8<-- "examples/custom_binary_type.output"
-    ```
-
-### Compatible containers
-
-| Container                                                                                   | Notes                                                                     |
-|---------------------------------------------------------------------------------------------|---------------------------------------------------------------------------|
-| `#!cpp std::vector<std::uint8_t>` (default)                                                 |                                                                           |
-| `#!cpp std::vector<char>`, `#!cpp std::vector<std::byte>`                                   | `dump()` writes the bytes as 0..255 whichever is used                     |
-| `boost::container::vector<std::uint8_t>`, `boost::container::small_vector<std::uint8_t, N>` |                                                                           |
-| `absl::InlinedVector<std::uint8_t, N>`                                                      | usable here, unlike as an `ArrayType`, because the value type is complete |
-| `eastl::vector<std::uint8_t>`                                                               | usable here, unlike as an `ArrayType`, because `max_size()` is not needed |
-| `folly::fbvector<std::uint8_t>`                                                             | requires C++20, see the note above                                        |
-
-### Containers that cannot be used
-
-| Container                                            | Reason                                                                                                                                                                                             |
-|------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| `QByteArray`                                         | no `empty()` (it spells that `isEmpty()`); its `insert` takes an index rather than an iterator; and it converts to `string_t`, which makes `to_json` ambiguous between a string and a binary value |
-| `#!cpp std::string`                                  | `binary_t::container_type` and `string_t` would be the same type, so the two [`swap`](../../api/basic_json/swap.md) overloads collide and `basic_json` cannot be instantiated at all               |
-| `#!cpp std::deque<std::uint8_t>`                     | storage is not contiguous, so there is no `data()`                                                                                                                                                 |
-| containers whose `value_type` is wider than one byte | see above -- accepted by the compiler, wrong at runtime                                                                                                                                            |
-
-## `CustomBaseClass`
-
-`CustomBaseClass` is an extension point: unless it is `#!cpp void` (the default, which selects the empty
-`nlohmann::json_default_base`), `basic_json` publicly derives from it.
-
-### Always required
-
- A non-`final`, default-constructible class type.
- `basic_json` is copy-/move-constructible and copy-/move-assignable only if `CustomBaseClass` is.
-
-### Notes
-
-`basic_json` is documented to be a
-[StandardLayoutType](https://en.cppreference.com/w/cpp/named_req/StandardLayoutType). Because `basic_json` has
-non-static data members of its own, a `CustomBaseClass` with non-static data members forfeits this guarantee.
-
-Note the namespace of `CustomBaseClass` becomes an associated namespace of `basic_json` for the purpose of
-argument-dependent lookup.
-
-See [`json_base_class_t`](../../api/basic_json/json_base_class_t.md) for an example.
-
-### Compatible types
-
-| Type                                         | Support                                                                    |
-|----------------------------------------------|----------------------------------------------------------------------------|
-| `#!cpp void` (default)                       | an empty base class is used; no effect on `basic_json`                     |
-| any default-constructible, non-`final` class | full; see [`json_base_class_t`](../../api/basic_json/json_base_class_t.md) |
-
-## Cross-specialization conversions
-
-Converting a value from one `basic_json` specialization into another (see the
-[converting constructor](../../api/basic_json/basic_json.md)) imposes two additional requirements that are not
-diagnosed at compile time. With assertions enabled they abort on the `#!cpp JSON_ASSERT` at the end of the converting
-constructor; under `#!cpp NDEBUG` they fail **silently** at runtime:
-
- The target `string_t` must be directly constructible from the source `string_t`. Otherwise the string is converted to
-  an array of character codes.
- The target `object_t::key_type` must be directly constructible from the source object's key type. Otherwise the
-  object is converted to an array of key/value pairs.
-
-See [issue #3425](https://github.com/nlohmann/json/issues/3425), [`string_t`](../../api/basic_json/string_t.md), and
-[`object_t`](../../api/basic_json/object_t.md).
-
-## See also
-
- [Types](index.md) -- overview of how JSON values are stored
- [Number Handling](number_handling.md) -- how the number types affect parsing and serialization
- [Object Order](../object_order.md) -- using an insertion-ordered `ObjectType`
- [`basic_json`](../../api/basic_json/index.md) -- API documentation of the class template
@@ -1,125 +1,34 @@
 # Architecture

-This page gives a high-level overview of the library's architecture. It should help new contributors to get an idea of
-the used concepts and where to make changes.
+!!! info
+
+    This page is still under construction. Its goal is to provide a high-level overview of the library's architecture.
+    This should help new contributors to get an idea of the used concepts and where to make changes.

 ## Overview

-The library is built around a single class template, [`nlohmann::basic_json`](../api/basic_json/index.md). A
-`basic_json` value is a node in a tree of JSON values. All other components either create such a tree from an input
-(parsing), write a tree to an output (serialization), or give access to it (iterators, JSON Pointer, conversions).
+The main structure is class [nlohmann::basic_json](../api/basic_json/index.md).

-```mermaid
-flowchart LR
-    input[/"input<br>(string, stream,<br>iterator range, file)"/]
-    ia["input adapter"]
-    lexer["lexer"]
-    parser["parser"]
-    breader["binary_reader"]
-    sax["SAX interface"]
-    value[("basic_json<br>value tree")]
-    serializer["serializer"]
-    bwriter["binary_writer"]
-    oa["output adapter"]
-    output[/"output<br>(string, stream,<br>vector)"/]
+- public API
+- container interface
+- iterators

-    input --> ia
-    ia --> lexer --> parser --> sax
-    ia --> breader --> sax
-    sax --> value
-    value --> serializer --> oa
-    value --> bwriter --> oa
-    oa --> output
-```
+## Template specializations

- **JSON text** is read by an [input adapter](#input-adapters), tokenized by the lexer, and turned into SAX events by
-  the parser.
- **Binary formats** (BJData, BSON, CBOR, MessagePack, UBJSON) are read by an input adapter and turned into the same SAX
-  events by the `binary_reader`.
- A [SAX consumer](#sax-interface) receives the events. The one used by [`parse`](../api/basic_json/parse.md) builds a
-  `basic_json` value tree.
- The `serializer` (JSON text) or the `binary_writer` (binary formats) writes a value tree to an
-  [output adapter](#output-adapters).
-
-## Source layout
-
-The public headers are in [`include/nlohmann`](https://github.com/nlohmann/json/tree/develop/include/nlohmann):
-
- [`json.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/json.hpp) defines class [`basic_json`](../api/basic_json/index.md).
- [`json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/json_fwd.hpp) contains forward declarations.
- [`adl_serializer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/adl_serializer.hpp), [`byte_container_with_subtype.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/byte_container_with_subtype.hpp), and [`ordered_map.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/ordered_map.hpp) define
-  [`adl_serializer`](../api/adl_serializer/index.md),
-  [`byte_container_with_subtype`](../api/byte_container_with_subtype/index.md), and
-  [`ordered_map`](../api/ordered_map.md).
-
-Everything else lives in [`detail/`](https://github.com/nlohmann/json/tree/develop/include/nlohmann/detail) and namespace `nlohmann::detail`, which is not part of the public API. Paths
-below are relative to `include/nlohmann`.
-
-| Component | Location |
-|-----------|----------|
-| Value type enumeration | [`detail/value_t.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/value_t.hpp) |
-| Input adapters | [`detail/input/input_adapters.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/input_adapters.hpp) |
-| Lexer | [`detail/input/lexer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/lexer.hpp), [`detail/input/number_parse.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/number_parse.hpp), [`detail/input/string_scan.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/string_scan.hpp) |
-| Parser | [`detail/input/parser.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/parser.hpp) |
-| SAX interface and DOM builders | [`detail/input/json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp) |
-| Binary format readers | [`detail/input/binary_reader.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/binary_reader.hpp) |
-| JSON serializer | [`detail/output/serializer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/output/serializer.hpp), [`detail/conversions/to_chars.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/conversions/to_chars.hpp) |
-| Binary format writers | [`detail/output/binary_writer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/output/binary_writer.hpp) |
-| Output adapters | [`detail/output/output_adapters.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/output/output_adapters.hpp) |
-| Iterators | [`detail/iterators/`](https://github.com/nlohmann/json/tree/develop/include/nlohmann/detail/iterators) |
-| Conversions from/to arbitrary types | [`detail/conversions/from_json.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/conversions/from_json.hpp), [`detail/conversions/to_json.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/conversions/to_json.hpp) |
-| JSON Pointer | [`detail/json_pointer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/json_pointer.hpp) |
-| Exceptions | [`detail/exceptions.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/exceptions.hpp) |
-| Type traits and C++ feature backports | [`detail/meta/`](https://github.com/nlohmann/json/tree/develop/include/nlohmann/detail/meta) |
-| Macros | [`detail/macro_scope.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/macro_scope.hpp), [`detail/macro_unscope.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/macro_unscope.hpp), [`detail/abi_macros.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/abi_macros.hpp) |
-
-The single-header version [`single_include/nlohmann/json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp)
-is generated from these files with `make amalgamate` and must not be edited by hand.
-
-## Template parameters
-
-[`basic_json`](../api/basic_json/index.md) is parameterized by the types it uses to store values and to convert from and to other types:
-
-| Template parameter   | Default                     | Used for                                                          |
-|----------------------|-----------------------------|-------------------------------------------------------------------|
-| `ObjectType`         | `std::map`                  | objects, see [`object_t`](../api/basic_json/object_t.md)          |
-| `ArrayType`          | `std::vector`               | arrays, see [`array_t`](../api/basic_json/array_t.md)             |
-| `StringType`         | `std::string`               | strings and object keys, see [`string_t`](../api/basic_json/string_t.md) |
-| `BooleanType`        | `bool`                      | Booleans, see [`boolean_t`](../api/basic_json/boolean_t.md)       |
-| `NumberIntegerType`  | `std::int64_t`              | signed integers, see [`number_integer_t`](../api/basic_json/number_integer_t.md) |
-| `NumberUnsignedType` | `std::uint64_t`             | unsigned integers, see [`number_unsigned_t`](../api/basic_json/number_unsigned_t.md) |
-| `NumberFloatType`    | `double`                    | floating-point numbers, see [`number_float_t`](../api/basic_json/number_float_t.md) |
-| `AllocatorType`      | `std::allocator`            | allocating objects, arrays, strings, and binary values            |
-| `JSONSerializer`     | `adl_serializer`            | conversions from/to other types, see [`adl_serializer`](../api/adl_serializer/index.md) |
-| `BinaryType`         | `std::vector<std::uint8_t>` | binary values, see [`binary_t`](../api/basic_json/binary_t.md)  |
-| `CustomBaseClass`    | `void`                      | an optional base class, see [`json_base_class_t`](../api/basic_json/json_base_class_t.md) |
-
-The library provides two specializations:
-
- [`json`](../api/json.md) uses all default template arguments.
- [`ordered_json`](../api/ordered_json.md) uses [`ordered_map`](../api/ordered_map.md) as `ObjectType` to keep the
-  insertion order of object keys.
-
-The requirements on the template arguments are listed in
-[Template Parameter Requirements](../features/types/template_parameters.md).
+- describe template parameters of `basic_json`
+- [`json`](../api/json.md)
+- [`ordered_json`](../api/ordered_json.md) via [`ordered_map`](../api/ordered_map.md)

 ## Value storage

-Each [`basic_json`](../api/basic_json/index.md) value stores its content as a tagged union: an enumeration [`value_t`](../api/basic_json/value_t.md)
-names the type of the value, and a union `json_value` holds the value itself. Both are members of the nested struct
-`data`, which is the only data member `m_data` of `basic_json`:
+Values are stored as a tagged union of [value_t](../api/basic_json/value_t.md) and json_value.

 ```cpp
-struct data
-{
-    /// the type of the current element
-    value_t m_type = value_t::null;
+/// the type of the current element
+value_t m_type = value_t::null;

-    /// the value of the current element
-    json_value m_value = {};
-};
-
-data m_data = {};
+/// the value of the current element
+json_value m_value = {};
 ```

 with
@@ -159,83 +68,42 @@ union json_value {
 };
 ```

-Objects, arrays, strings, and binary values are allocated on the heap with `AllocatorType`, and the union only stores a
-pointer to them. This keeps a `basic_json` value small: one pointer-sized union and one byte for the type. The class
-maintains the invariant that the pointer matching `m_type` is never null; `assert_invariant()` checks it with
-[runtime assertions](../features/assertions.md).
+## Parsing inputs (deserialization)

-## Input adapters
-
-Input is read via **input adapters** that abstract a source. Every input adapter provides this interface:
+Input is read via **input adapters** that abstract a source with a common interface:

 ```cpp
-/// the type of the characters in the input
-using char_type = ...;
+/// read a single character
+std::char_traits<char>::int_type get_character() noexcept;

-/// read a single character; returns std::char_traits<char_type>::eof() at the end of the input
-typename std::char_traits<char_type>::int_type get_character();
-
-/// read up to count * sizeof(T) bytes into dest and return the number of bytes read
-/// (used by the binary readers)
+/// read multiple characters to a destination buffer and
+/// returns the number of characters successfully read
 template<class T>
 std::size_t get_elements(T* dest, std::size_t count = 1);
 ```

-The lexer detects two optional extensions at compile time. Only `iterator_input_adapter` provides them, and only for
-random-access input of single-byte characters:
+List examples of input adapters.

- `supports_seek`, `get_consumed_count()`, and `copy_consumed_range()` let the lexer reconstruct already consumed input
-  for error messages instead of copying every character it reads.
- `supports_bulk_scan`, `bulk_data()`, `bulk_remaining()`, and `bulk_skip()` let the lexer scan strings directly in
-  contiguous memory, several bytes at a time.
+## SAX Interface

-The function `input_adapter` picks the right adapter for the argument passed to `parse`, `accept`, `sax_parse`, or the
-`from_*` functions:
+TODO

- `iterator_input_adapter` reads from an iterator range, which also covers strings, containers, and pointers.
- `wide_string_input_adapter` reads from ranges of `wchar_t`, `char16_t`, or `char32_t` and converts them to UTF-8.
-  It cannot be used for binary formats; its `get_elements()` throws.
- `input_stream_adapter` reads from a `std::istream`.
- `file_input_adapter` reads from a `std::FILE*`.
-
-## SAX interface
-
-The parser does not build values itself. It reports what it reads as events to a [SAX](../features/parsing/sax_interface.md)
-consumer, which implements the interface [`json_sax`](../api/json_sax/index.md): `null`, `boolean`, `number_integer`,
-`number_unsigned`, `number_float`, `string`, `binary`, `start_object`, `key`, `end_object`, `start_array`, `end_array`,
-and `parse_error`.
-
-The library comes with two consumers in `detail/input/json_sax.hpp`:
-
- `json_sax_dom_parser` builds a [`basic_json`](../api/basic_json/index.md) value tree. [`parse`](../api/basic_json/parse.md) uses it.
- `json_sax_dom_callback_parser` does the same, but calls a [parser callback](../features/parsing/parser_callbacks.md)
-  for each event, which can skip values. `parse` uses it when a callback is given.
-
-The `binary_reader` emits the same events for binary formats, so [`sax_parse`](../api/basic_json/sax_parse.md) works
-with a user-defined consumer for JSON and for all binary formats alike.
-
-## Output adapters
+## Writing outputs (serialization)

 Output is written via **output adapters**:

 ```cpp
+template<typename T>
 void write_character(CharType c);

+template<typename CharType>
 void write_characters(const CharType* s, std::size_t length);
 ```

-The `serializer` (used by [`dump`](../api/basic_json/dump.md) and [`operator<<`](../api/operator_ltlt.md)) and the
-`binary_writer` (used by the `to_*` functions) write to one of these adapters:
-
- `output_vector_adapter` appends to a `std::vector`.
- `output_stream_adapter` writes to a `std::ostream`.
- `output_string_adapter` appends to a string.
+List examples of output adapters.

 ## Value conversion

-Values are converted from and to other types with the `JSONSerializer` template parameter. The default,
-[`adl_serializer`](../api/adl_serializer/index.md), calls the free functions
-
 ```cpp
 template<class T>
 void to_json(basic_json& j, const T& t);
@@ -244,23 +112,13 @@ template<class T>
 void from_json(const basic_json& j, T& t);
 ```

-found by argument-dependent lookup. The library defines them for standard types in `detail/conversions`; users add them
-for their own types, see [Arbitrary Type Conversions](../features/arbitrary_types.md). The
-[serialization macros](../features/macros.md) generate these functions.
-
 ## Additional features

- [JSON Pointer](../features/json_pointer.md) (class `json_pointer`) addresses values inside a tree. It is also the
-  basis of [JSON Patch](../features/json_patch.md).
- [Binary formats](../features/binary_formats/index.md) are read by `binary_reader` and written by `binary_writer`.
- A [custom base class](../api/basic_json/json_base_class_t.md) can add members to every [`basic_json`](../api/basic_json/index.md) value.
- [Serialization macros](../features/macros.md) generate `to_json` and `from_json` functions for user-defined types.
+- JSON Pointers
+- Binary formats
+- Custom base class
+- Conversion macros

 ## Details namespace

-Namespace `nlohmann::detail` contains all implementation details. It is not part of the public API and may change in any
-release. Besides the components above, it contains:
-
- type traits to detect the capabilities of user-defined types (`detail/meta/type_traits.hpp`),
- backports of C++14/17 features to C++11 (`detail/meta/cpp_future.hpp`), and
- helpers such as `string_concat` and `string_escape`.
+- C++ feature backports
@@ -340,7 +340,8 @@ An unexpected byte was read in a [binary format](../features/binary_formats/inde
 ### json.exception.parse_error.113

 A string could not be read from a [binary format](../features/binary_formats/index.md): either a value that is not a
-string was read where one was required (for instance as a map key), or the string's length specification is invalid.
+string was read where one was required (for instance as a map key), the string's length specification is invalid, or
+the string's bytes are not valid UTF-8.

 !!! failure "Example messages"

@@ -356,6 +357,9 @@ string was read where one was required (for instance as a map key), or the strin
    ```
    [json.exception.parse_error.113] parse error at byte 3: syntax error while parsing BJData string: string length must not be negative
    ```
+    ```
+    [json.exception.parse_error.113] parse error at byte 3: syntax error while parsing CBOR string: invalid string: ill-formed UTF-8 byte
+    ```

 ### json.exception.parse_error.114

@@ -970,21 +974,6 @@ A JSON Patch `move` operation's `"from"` location is a proper prefix of its `"pa

    This exception was added in version 3.13.0. Before that, this situation could succeed with a corrupted result: for an array target, removing the "from" element before the "add" step shifted subsequent indices, so "path" silently re-resolved to a different element than intended.

-### json.exception.out_of_range.415
-
-MessagePack's ext type and BSON's binary subtype are each stored in a single byte. This exception is thrown when serializing a
-[`byte_container_with_subtype`](../api/byte_container_with_subtype/index.md) whose subtype exceeds 255.
-
-!!! failure "Example message"
-
-    ```
-    [json.exception.out_of_range.415] subtype 70000 is too large for the MessagePack ext type (max 255)
-    ```
-
-!!! note
-
-    This exception was added in version 3.13.0. Before that, subtypes above 255 were silently truncated modulo 256 instead of raising an error.
-
 ## Further exceptions

 This exception is thrown in case of errors that cannot be classified with the
@@ -90,54 +90,6 @@ The library supports **Unicode input** as follows:
 In most cases, the parser is right to complain, because the input is not UTF-8 encoded. This is especially true for Microsoft Windows, where Latin-1 or ISO 8859-1 is often the standard encoding.


-### NUL bytes in the input
-
-!!! question "Questions"
-
-    - Why does `json::parse()` silently ignore part of my input?
-    - Why does a `std::string`/buffer with extra data after the JSON text parse without error, while a similar-looking string with extra text does not?
-
-A `'\0'` (NUL) byte anywhere in the input is treated the same as the real end of the input, rather than as an ordinary (and, outside of a string, invalid) byte. Everything from that byte onward is silently ignored, without a parse error — including further, otherwise well-formed JSON:
-
-```cpp
-json::parse(std::string("123") + '\0');          // == 123, no error
-json::parse(std::string("123") + '\0' + "true"); // == 123, the "true" is silently ignored too
-```
-
-This is different from any other unexpected trailing byte, which *does* raise [`parse_error.101`](../home/exceptions.md#jsonexceptionparse_error101):
-
-```cpp
-json::parse("123x"); // throws parse_error.101: unexpected additional data
-```
-
-This falls out of the same convention used when no explicit input length is given at all: `json::parse(const char*)` already stops at the first NUL byte via `strlen()`, since a bare pointer has no length of its own. The library applies that same NUL-terminated-C-string convention uniformly, rather than only when a length is genuinely unavailable — so a `std::string`, iterator range, or container whose content happens to include a NUL byte is affected the same way a raw `const char*` would be.
-
-If your input may contain a trailing or embedded NUL that is **not** meant to signal the end of the JSON text — for instance, a fixed-size, zero-padded buffer — trim it yourself before calling `parse()`, since the library will otherwise silently stop there instead of raising an error:
-
-```cpp
-s.resize(s.find('\0')); // drop everything from the first NUL onward, if any
-json::parse(s);
-```
-
-**Opt-in strict handling (since version 3.13.0)**
-
-Manually trimming every input is easy to forget. If you define [`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md) to `1` before including the library, a `'\0'` byte is instead rejected like any other unexpected byte and raises `parse_error.101`, instead of being treated as end of input:
-
-```cpp
-#define JSON_STRICT_NUL_HANDLING 1
-#include <nlohmann/json.hpp>
-
-json::parse(std::string("123") + '\0'); // throws parse_error.101 instead of silently returning 123
-```
-
-This macro defaults to `0` (disabled, preserving the behavior described above) to avoid breaking existing code that may depend on it, even unknowingly; it is planned to become the default in version 4.0.0. See [its documentation](../api/macros/json_strict_nul_handling.md) for details, including how it also affects `char` arrays such as string literals.
-
-Note that this is unrelated to an *unescaped* NUL byte occurring **inside** a quoted JSON string, which is a different, already-invalid case and is correctly rejected either way:
-
-```cpp
-json::parse(std::string("\"") + '\0' + "\""); // throws parse_error.101: control character U+0000 (NUL) must be escaped to \u0000
-```
-
 ### Wide string handling

 !!! question
@@ -198,11 +198,6 @@ Use the non-amalgamated version of the library. This option is `ON` by default.

 Treat the library headers like system headers (i.e., adding `SYSTEM` to the [`target_include_directories`](https://cmake.org/cmake/help/latest/command/target_include_directories.html) call) to check for this library by tools like Clang-Tidy. This option is `OFF` by default.

-### `JSON_StrictNulHandling`
-
-Reject a `'\0'` (NUL) byte in the input instead of treating it as end of input, by defining the macro
-[`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md). This option is `OFF` by default.
-
 ### `JSON_Valgrind`

 Execute the test suite with [Valgrind](https://valgrind.org). This option is `OFF` by default. Depends on `JSON_BuildTests`.
@@ -176,12 +176,6 @@ You can prepare existing code by already defining
 conversions with calls to [`get`](../api/basic_json/get.md), [`get_to`](../api/basic_json/get_to.md),
 [`get_ref`](../api/basic_json/get_ref.md), or [`get_ptr`](../api/basic_json/get_ptr.md).

-!!! tip "Automatic migration"
-
-    The community-maintained clang-tidy check `modernize-nlohmann-json-explicit-conversions` rewrites most implicit
-    conversions into calls to [`get`](../api/basic_json/get.md). It is not part of clang-tidy itself; see
-    [discussion #4610](https://github.com/nlohmann/json/discussions/4610) for how to build and use it.
-
 === "Deprecated"

      ```cpp
@@ -98,7 +98,6 @@ nav:
      - Types:
          - features/types/index.md
          - features/types/number_handling.md
-          - features/types/template_parameters.md
  - Integration:
      - integration/index.md
      - integration/migration_guide.md
@@ -292,11 +291,8 @@ nav:
          - 'JSON_HAS_THREE_WAY_COMPARISON': api/macros/json_has_three_way_comparison.md
          - 'JSON_NOEXCEPTION': api/macros/json_noexception.md
          - 'JSON_NO_IO': api/macros/json_no_io.md
-          - 'JSON_NO_THREAD_LOCAL': api/macros/json_no_thread_local.md
-          - 'JSON_PRECISE_STREAM_POSITION': api/macros/json_precise_stream_position.md
          - 'JSON_SKIP_LIBRARY_VERSION_CHECK': api/macros/json_skip_library_version_check.md
          - 'JSON_SKIP_UNSUPPORTED_COMPILER_CHECK': api/macros/json_skip_unsupported_compiler_check.md
-          - 'JSON_STRICT_NUL_HANDLING': api/macros/json_strict_nul_handling.md
          - 'JSON_USE_GLOBAL_UDLS': api/macros/json_use_global_udls.md
          - 'JSON_USE_IMPLICIT_CONVERSIONS': api/macros/json_use_implicit_conversions.md
          - 'JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON': api/macros/json_use_legacy_discarded_value_comparison.md
@@ -318,9 +314,7 @@ nav:
      - community/contribution_guidelines.md
      - community/quality_assurance.md
      - community/governance.md
-      - community/roadmap.md
      - community/security_policy.md
-      - community/assurance_case.md

 # Extras
 extra:
@@ -1,7 +1,7 @@
 wheel==0.48.0

 mkdocs==1.6.1                                       # documentation framework
-mkdocs-git-revision-date-localized-plugin==1.6.0    # plugin "git-revision-date-localized"
+mkdocs-git-revision-date-localized-plugin==1.5.4    # plugin "git-revision-date-localized"
 mkdocs-material==9.7.7                             # theme for mkdocs
 mkdocs-material-extensions==1.3.1                   # extensions
 mkdocs-minify-plugin==0.8.0                         # plugin "minify"
@@ -34,14 +34,6 @@
    #define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 0
 #endif

-#ifndef JSON_BRACE_INIT_COPY_SEMANTICS
-    #define JSON_BRACE_INIT_COPY_SEMANTICS 0
-#endif
-
-#ifndef JSON_PRECISE_STREAM_POSITION
-    #define JSON_PRECISE_STREAM_POSITION 0
-#endif
-
 #if JSON_DIAGNOSTICS
    #define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
 #else
@@ -60,34 +52,20 @@
    #define NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON
 #endif

-#if JSON_BRACE_INIT_COPY_SEMANTICS
-    #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS _bics
-#else
-    #define NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS
-#endif
-
-#if JSON_PRECISE_STREAM_POSITION
-    #define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION _psp
-#else
-    #define NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION
-#endif
-
 #ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
    #define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
 #endif

 // Construct the namespace ABI tags component
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e) json_abi ## a ## b ## c ## d ## e
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e)
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c) json_abi ## a ## b ## c
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c) \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c)

 #define NLOHMANN_JSON_ABI_TAGS                                       \
    NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
            NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
            NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
-            NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS,              \
-            NLOHMANN_JSON_ABI_TAG_BRACE_INIT_COPY_SEMANTICS,         \
-            NLOHMANN_JSON_ABI_TAG_PRECISE_STREAM_POSITION)
+            NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS)

 // Construct the namespace version component
 #define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \
@@ -471,30 +471,6 @@ inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& t, index_sequence<
    j = { std::get<Idx>(t)... };
 }

-#if JSON_BRACE_INIT_COPY_SEMANTICS
-// JSON_BRACE_INIT_COPY_SEMANTICS makes a one-element braced list copy its
-// element instead of wrapping it, which would serialize std::tuple<int>{5} as 5
-// rather than [5]. Build what the default deduction builds instead: an object
-// if the element is a [string, value] pair, a one-element array otherwise.
-template<typename BasicJsonType, typename Tuple>
-inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& t, index_sequence<0> /*unused*/)
-{
-    BasicJsonType element(std::get<0>(t));
-    // same test as the initializer-list constructor, including the cast that
-    // keeps a string type constructible from 0 from selecting operator[](key)
-    const bool is_member = element.is_array() && element.size() == 2
-                           && element[static_cast<typename BasicJsonType::size_type>(0)].is_string();
-    if (is_member)
-    {
-        j = BasicJsonType::object({std::move(element)});
-    }
-    else
-    {
-        j = BasicJsonType::array({std::move(element)});
-    }
-}
-#endif
-
 template<typename BasicJsonType, typename Tuple>
 inline void to_json_tuple_impl(BasicJsonType& j, const Tuple& /*unused*/, index_sequence<> /*unused*/)
 {
@@ -101,10 +101,7 @@ class exception : public std::exception
                    {
                        if (&element.second == current)
                        {
-                            // data() is null-terminated, so a key containing
-                            // a null byte is cut short here rather than
-                            // truncating the whole message at what()
-                            tokens.emplace_back(element.first.data());
+                            tokens.emplace_back(element.first.c_str());
                            break;
                        }
                    }
@@ -11,10 +11,8 @@
 #include <cstdint> // uint8_t
 #include <cstddef> // size_t
 #include <functional> // hash
-#include <vector> // vector

 #include <nlohmann/detail/abi_macros.hpp>
-#include <nlohmann/detail/recursion_depth_limit.hpp>
 #include <nlohmann/detail/value_t.hpp>

 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -28,9 +26,6 @@ inline std::size_t combine(std::size_t seed, std::size_t h) noexcept
    return seed;
 }

-template<typename BasicJsonType>
-std::size_t hash_iteratively(const BasicJsonType& j);
-
 /*!
@brief hash a JSON value

@@ -38,21 +33,12 @@ The hash function tries to rely on std::hash where possible. Furthermore, the
 type of the JSON value is taken into account to have different hash values for
 null, 0, 0U, and false, etc.

-Hashing an array or an object hashes its elements, which used to call this
-function again once per nesting level, so a value nested deeply enough
-exhausted the call stack and terminated the process. The descent is bounded
-here: once @ref recursion_depth_limit levels have been entered, @ref
-hash_iteratively hashes what is left without the call stack. A value nested
-less deeply than that - all but a vanishing minority - is hashed exactly as
-before, without allocating.
-
@tparam BasicJsonType basic_json specialization
@param j JSON value to hash
-@param depth nesting level of @a j, counted from the value passed by the caller
@return hash value of j
 */
 template<typename BasicJsonType>
-std::size_t hash(const BasicJsonType& j, const std::size_t depth = 0)
+std::size_t hash(const BasicJsonType& j)
 {
    using string_t = typename BasicJsonType::string_t;
    using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -70,32 +56,22 @@ std::size_t hash(const BasicJsonType& j, const std::size_t depth = 0)

        case BasicJsonType::value_t::object:
        {
-            if (JSON_HEDLEY_UNLIKELY(depth >= recursion_depth_limit()))
-            {
-                return hash_iteratively(j);
-            }
-
            auto seed = combine(type, j.size());
            for (const auto& element : j.items())
            {
                const auto h = std::hash<string_t> {}(element.key());
                seed = combine(seed, h);
-                seed = combine(seed, hash(element.value(), depth + 1));
+                seed = combine(seed, hash(element.value()));
            }
            return seed;
        }

        case BasicJsonType::value_t::array:
        {
-            if (JSON_HEDLEY_UNLIKELY(depth >= recursion_depth_limit()))
-            {
-                return hash_iteratively(j);
-            }
-
            auto seed = combine(type, j.size());
            for (const auto& element : j)
            {
-                seed = combine(seed, hash(element, depth + 1));
+                seed = combine(seed, hash(element));
            }
            return seed;
        }
@@ -138,9 +114,7 @@ std::size_t hash(const BasicJsonType& j, const std::size_t depth = 0)
            seed = combine(seed, static_cast<std::size_t>(j.get_binary().subtype()));
            for (const auto byte : j.get_binary())
            {
-                // the cast is needed for binary types whose value type is not
-                // an integer (e.g., std::byte)
-                seed = combine(seed, std::hash<std::uint8_t> {}(static_cast<std::uint8_t>(byte)));
+                seed = combine(seed, std::hash<std::uint8_t> {}(byte));
            }
            return seed;
        }
@@ -151,77 +125,5 @@ std::size_t hash(const BasicJsonType& j, const std::size_t depth = 0)
    }
 }

-/// an array or object whose elements @ref hash_iteratively is hashing
-template<typename BasicJsonType>
-struct hash_frame
-{
-    hash_frame(const BasicJsonType* value_, std::size_t seed_) noexcept
-        : value(value_), position(value_->cbegin()), seed(seed_)
-    {}
-
-    const BasicJsonType* value;
-    typename BasicJsonType::const_iterator position;
-    std::size_t seed;
-};
-
-/*!
-@brief hash the array or object @a j without the call stack
-
-Computes the same value as @ref hash, keeping the arrays and objects it has
-entered on an explicit stack instead of descending into them. Only reached for
-values nested deeper than @ref recursion_depth_limit.
-
-@tparam BasicJsonType basic_json specialization
-@param j array or object to hash
-@return hash value of j
-*/
-template<typename BasicJsonType>
-std::size_t hash_iteratively(const BasicJsonType& j)
-{
-    using string_t = typename BasicJsonType::string_t;
-
-    std::vector<hash_frame<BasicJsonType>> stack;
-    stack.emplace_back(&j, combine(static_cast<std::size_t>(j.type()), j.size()));
-
-    while (true)
-    {
-        // a copy, as entering an element below can reallocate the stack; the
-        // frame itself is only changed through stack.back()
-        const hash_frame<BasicJsonType> frame = stack.back();
-
-        if (frame.position == frame.value->cend())
-        {
-            // all elements are hashed: fold this value's hash into its parent's
-            // seed, exactly where the recursive version returns it
-            const std::size_t h = frame.seed;
-            stack.pop_back();
-            if (stack.empty())
-            {
-                return h;
-            }
-            stack.back().seed = combine(stack.back().seed, h);
-            continue;
-        }
-
-        if (frame.value->is_object())
-        {
-            stack.back().seed = combine(stack.back().seed, std::hash<string_t> {}(frame.position.key()));
-        }
-
-        // advance before entering the element, which pushes onto the stack
-        const BasicJsonType& element = *frame.position;
-        ++stack.back().position;
-
-        if (element.is_structured())
-        {
-            stack.emplace_back(&element, combine(static_cast<std::size_t>(element.type()), element.size()));
-        }
-        else
-        {
-            stack.back().seed = combine(stack.back().seed, hash(element));
-        }
-    }
-}
-
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
@@ -32,6 +32,7 @@
 #include <nlohmann/detail/meta/is_sax.hpp>
 #include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/string_concat.hpp>
+#include <nlohmann/detail/string_utils.hpp>
 #include <nlohmann/detail/value_t.hpp>

 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -432,7 +433,21 @@ class binary_reader
                                    exception_message(input_format_t::bson, concat("string length must be at least 1, is ", std::to_string(len)), "string"), nullptr));
        }

-        return get_string(input_format_t::bson, len - static_cast<NumberType>(1), result) && get() != char_traits<char_type>::eof();
+        if (JSON_HEDLEY_UNLIKELY(!get_string(input_format_t::bson, len - static_cast<NumberType>(1), result)))
+        {
+            return false;
+        }
+
+        if (JSON_HEDLEY_UNLIKELY(get() != 0x00))
+        {
+            auto last_token = get_token_string();
+            return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                    exception_message(input_format_t::bson,
+                                            "BSON string is not null-terminated",
+                                            "string"), nullptr));
+        }
+
+        return true;
    }

    /*!
@@ -550,8 +565,6 @@ class binary_reader
        }
    }

-
-
    //////////
    // CBOR //
    //////////
@@ -3146,10 +3159,7 @@ class binary_reader
                               number_string,
                               out_of_range::create(406, concat("number overflow parsing '", number_string, '\''), nullptr));
                }
-                // number_string is a std::string, while the SAX interface takes a
-                // string_t; convert explicitly, as the two are only implicitly
-                // convertible for some string types
-                return sax->number_float(parsed_float, string_t(number_string.data(), number_string.size()));
+                return sax->number_float(parsed_float, std::move(number_string));
            }
            case token_type::uninitialized:
            case token_type::literal_true:
@@ -3304,7 +3314,28 @@ class binary_reader
                    const NumberType len,
                    string_t& result)
    {
-        return get_bytes(format, len, "string", result);
+        // get_bytes() appends to result, and CBOR indefinite-length strings
+        // collect all their chunks in the same result; validating only the
+        // newly read bytes keeps the check linear in the input size
+        const std::size_t old_size = result.size();
+        if (JSON_HEDLEY_UNLIKELY(!get_bytes(format, len, "string", result)))
+        {
+            return false;
+        }
+
+        // RFC 8949 (CBOR) §3.1 and the MessagePack/BSON/UBJSON specifications
+        // all require text strings to be valid UTF-8; reject anything else
+        // right here so malformed input is caught at decode time instead of
+        // only surfacing later as a type_error.316 when the value is dumped
+        // (which would defeat allow_exceptions=false / strict discarding).
+        if (JSON_HEDLEY_UNLIKELY(!is_valid_utf8(result, old_size)))
+        {
+            return sax->parse_error(chars_read, get_token_string(),
+                                    parse_error::create(113, chars_read,
+                                            exception_message(format, "invalid string: ill-formed UTF-8 byte", "string"), nullptr));
+        }
+
+        return true;
    }

    /*!
@@ -101,11 +101,6 @@ class input_stream_adapter
        // maintain ifstream flags, except eof
        if (is != nullptr)
        {
-#if JSON_PRECISE_STREAM_POSITION
-            // consume the character last returned by get_character() unless it
-            // was given back with release_lookahead()
-            commit_lookahead();
-#endif
            is->clear(is->rdstate() & std::ios::eofbit);
        }
    }
@@ -119,58 +114,6 @@ class input_stream_adapter
    input_stream_adapter& operator=(input_stream_adapter&) = delete;
    input_stream_adapter& operator=(input_stream_adapter&&) = delete;

-#if JSON_PRECISE_STREAM_POSITION
-    input_stream_adapter(input_stream_adapter&& rhs) noexcept
-        : is(rhs.is), sb(rhs.sb), lookahead(rhs.lookahead)
-    {
-        rhs.is = nullptr;
-        rhs.sb = nullptr;
-        rhs.lookahead = false;
-    }
-
-    // Whether the character last returned by get_character() can be given back
-    // to the input with release_lookahead().
-    static constexpr bool supports_lookahead = true;
-
-    // std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
-    // ensure that std::char_traits<char>::eof() and the character 0xFF do not
-    // end up as the same value, e.g., 0xFFFFFFFF.
-    //
-    // The character is peeked rather than consumed: it is only stepped over
-    // once the next character is requested, or when the adapter is destroyed.
-    // Until then, release_lookahead() can leave it in the input.
-    std::char_traits<char>::int_type get_character()
-    {
-        if (lookahead)
-        {
-            // step over the character returned by the previous call
-            sb->sbumpc();
-        }
-
-        auto res = sb->sgetc();
-        // set eof manually, as we don't use the istream interface.
-        if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof()))
-        {
-            // there is nothing to step over next time
-            lookahead = false;
-            is->clear(is->rdstate() | std::ios::eofbit);
-        }
-        else
-        {
-            lookahead = true;
-        }
-        return res;
-    }
-
-    // Leave the character last returned by get_character() in the input, so
-    // that the next read from the stream - by this adapter or by the caller
-    // once parsing is done - sees it again. Unlike putting a consumed
-    // character back, this cannot fail.
-    void release_lookahead() noexcept
-    {
-        lookahead = false;
-    }
-#else
    input_stream_adapter(input_stream_adapter&& rhs) noexcept
        : is(rhs.is), sb(rhs.sb)
    {
@@ -181,9 +124,6 @@ class input_stream_adapter
    // std::istream/std::streambuf use std::char_traits<char>::to_int_type, to
    // ensure that std::char_traits<char>::eof() and the character 0xFF do not
    // end up as the same value, e.g., 0xFFFFFFFF.
-    //
-    // The character is consumed, so the character that terminates a number
-    // stays consumed after parsing; see JSON_PRECISE_STREAM_POSITION.
    std::char_traits<char>::int_type get_character()
    {
        auto res = sb->sbumpc();
@@ -194,14 +134,10 @@ class input_stream_adapter
        }
        return res;
    }
-#endif

    template<class T>
    std::size_t get_elements(T* dest, std::size_t count = 1)
    {
-#if JSON_PRECISE_STREAM_POSITION
-        commit_lookahead();
-#endif
        auto res = static_cast<std::size_t>(sb->sgetn(reinterpret_cast<char*>(dest), static_cast<std::streamsize>(count * sizeof(T))));
        if (JSON_HEDLEY_UNLIKELY(res < count * sizeof(T)))
        {
@@ -211,27 +147,9 @@ class input_stream_adapter
    }

  private:
-#if JSON_PRECISE_STREAM_POSITION
-    // Step over the character last returned by get_character(). The character
-    // has already been peeked successfully, so for every streambuf with a get
-    // area this is a pointer increment that cannot fail.
-    void commit_lookahead()
-    {
-        if (lookahead)
-        {
-            lookahead = false;
-            sb->sbumpc();
-        }
-    }
-#endif
-
    /// the associated input stream
    std::istream* is = nullptr;
    std::streambuf* sb = nullptr;
-#if JSON_PRECISE_STREAM_POSITION
-    /// whether get_character() peeked a character that is not consumed yet
-    bool lookahead = false;
-#endif
 };
 #endif  // JSON_NO_IO

@@ -844,21 +762,6 @@ contiguous_bytes_input_adapter input_adapter(CharT b)
 template<typename T, std::size_t N>
 auto input_adapter(T (&array)[N]) -> decltype(input_adapter(array, array + N)) // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
 {
-#if JSON_STRICT_NUL_HANDLING
-    // A `char` array from string-literal initialization (e.g. json::parse("123"))
-    // carries a trailing '\0' contributed by the compiler, not by the source
-    // text; drop exactly that one byte so it is not mistaken for real trailing
-    // data. Every other element type (unsigned char, std::uint8_t, ...) keeps
-    // the full extent unconditionally, since a trailing zero byte there is
-    // genuine data (e.g. CBOR/MessagePack). This intentionally does not
-    // strlen()-scan the array (as the pointer overload above does for a
-    // null-delimited string): for a `char` array that is not NUL-terminated
-    // within its bounds, that would read past the end of the array.
-    if (std::is_same<typename std::remove_cv<T>::type, char>::value && N > 0 && array[N - 1] == 0)
-    {
-        return input_adapter(array, array + N - 1);
-    }
-#endif
    return input_adapter(array, array + N);
 }

@@ -8,11 +8,11 @@

 #pragma once

-#include <algorithm> // find_if, min
+#include <algorithm> // min
 #include <cstddef>
 #include <string> // string
 #include <type_traits> // enable_if_t
-#include <utility> // move, pair
+#include <utility> // move
 #include <vector> // vector

 #include <nlohmann/detail/exceptions.hpp>
@@ -278,7 +278,7 @@ class json_sax_dom_parser

        if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
        {
-            return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
+            JSON_THROW(out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
        }

        return true;
@@ -327,7 +327,7 @@ class json_sax_dom_parser

        if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
        {
-            return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
+            JSON_THROW(out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
        }

        if (len != detail::unknown_size())
@@ -611,7 +611,7 @@ class json_sax_dom_callback_parser
            // check object limit
            if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
            {
-                return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
+                JSON_THROW(out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
            }
        }
        return true;
@@ -631,17 +631,7 @@ class json_sax_dom_callback_parser
        // add discarded value at the given key and store the reference for later
        if (keep && ref_stack.back())
        {
-            auto& obj = *ref_stack.back()->m_data.m_value.object;
-            const auto it = obj.find(val);
-            if (it != obj.end())
-            {
-                // this is a duplicate key (legal in JSON); remember its
-                // current value so it can be restored later if the new
-                // value is rejected by the callback, instead of being
-                // erased together with the discarded placeholder
-                duplicate_key_stash.emplace_back(&(it->second), it->second);
-            }
-            object_element = &(obj[val] = discarded);
+            object_element = &(ref_stack.back()->m_data.m_value.object->operator[](val) = discarded);
        }

        return true;
@@ -653,18 +643,13 @@ class json_sax_dom_callback_parser
        {
            if (!callback(static_cast<int>(ref_stack.size()) - 1, parse_event_t::object_end, *ref_stack.back()))
            {
-                // discard object, unless this slot holds a duplicate key's
-                // previous value pending restoration, in which case that
-                // value is restored instead of being discarded
-                if (!resolve_duplicate_key_stash(ref_stack.back(), true))
-                {
-                    *ref_stack.back() = discarded;
+                // discard object
+                *ref_stack.back() = discarded;

 #if JSON_DIAGNOSTIC_POSITIONS
-                    // Set start/end positions for discarded object.
-                    handle_diagnostic_positions_for_json_value(*ref_stack.back());
+                // Set start/end positions for discarded object.
+                handle_diagnostic_positions_for_json_value(*ref_stack.back());
 #endif
-                }
            }
            else
            {
@@ -678,10 +663,6 @@ class json_sax_dom_callback_parser
 #endif

                ref_stack.back()->set_parents();
-                // this object is finally, definitively kept; drop any
-                // pending duplicate-key stash entry for its slot since it
-                // can no longer be restored
-                resolve_duplicate_key_stash(ref_stack.back(), false);
            }
        }

@@ -730,7 +711,7 @@ class json_sax_dom_callback_parser
            // check array limit
            if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
            {
-                return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
+                JSON_THROW(out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
            }

            if (len != detail::unknown_size())
@@ -762,25 +743,16 @@ class json_sax_dom_callback_parser
 #endif

                ref_stack.back()->set_parents();
-                // this array is finally, definitively kept; drop any
-                // pending duplicate-key stash entry for its slot since it
-                // can no longer be restored
-                resolve_duplicate_key_stash(ref_stack.back(), false);
            }
            else
            {
-                // discard array, unless this slot holds a duplicate key's
-                // previous value pending restoration, in which case that
-                // value is restored instead of being discarded
-                if (!resolve_duplicate_key_stash(ref_stack.back(), true))
-                {
-                    *ref_stack.back() = discarded;
+                // discard array
+                *ref_stack.back() = discarded;

 #if JSON_DIAGNOSTIC_POSITIONS
-                    // Set start/end positions for discarded array.
-                    handle_diagnostic_positions_for_json_value(*ref_stack.back());
+                // Set start/end positions for discarded array.
+                handle_diagnostic_positions_for_json_value(*ref_stack.back());
 #endif
-                }
            }
        }

@@ -897,35 +869,6 @@ class json_sax_dom_callback_parser
    }
 #endif

-    /// if there is a pending duplicate-key stash entry for this exact slot,
-    /// remove it from the stash; if restore_value is true, the stashed
-    /// previous value is moved back into the slot first (use this when the
-    /// new value at that slot was rejected); otherwise the stash entry is
-    /// simply dropped (use this when the new value was accepted, so it
-    /// correctly supersedes the old one and no restore should ever happen
-    /// for this slot again)
-    /// @return whether a matching stash entry was found (and processed)
-    bool resolve_duplicate_key_stash(BasicJsonType* slot, bool restore_value)
-    {
-        const auto it = std::find_if(duplicate_key_stash.begin(), duplicate_key_stash.end(),
-                                     [slot](const std::pair<BasicJsonType*, BasicJsonType>& entry)
-        {
-            return entry.first == slot;
-        });
-
-        if (it == duplicate_key_stash.end())
-        {
-            return false;
-        }
-
-        if (restore_value)
-        {
-            *slot = std::move(it->second);
-        }
-        duplicate_key_stash.erase(it);
-        return true;
-    }
-
    /*!
    @brief the key the value now being handled will be stored under

@@ -944,9 +887,7 @@ class json_sax_dom_callback_parser
    }

    /*!
-    @brief remove the discarded value the callback rejected from its parent,
-    unless it is a duplicate key's slot with a stashed previous value, in
-    which case that previous value is restored instead
+    @brief remove the discarded value the callback rejected from its parent

    A rejected value can only ever be the one most recently added to @a parent:
    the last element of an array, or the placeholder key() stored under @a key
@@ -961,7 +902,7 @@ class json_sax_dom_callback_parser
    @param[in,out] parent  the container to remove the rejected value from
    @param[in] key  the key the value was stored under; unused for arrays
    */
-    void remove_discarded_value(BasicJsonType& parent, const string_t& key)
+    static void remove_discarded_value(BasicJsonType& parent, const string_t& key)
    {
        if (parent.is_array())
        {
@@ -977,12 +918,7 @@ class json_sax_dom_callback_parser
            const auto it = object.find(key);
            if (it != object.end() && it->second.is_discarded())
            {
-                // a duplicate key's slot has a stashed previous value that
-                // must be restored instead of being erased
-                if (!resolve_duplicate_key_stash(&it->second, true))
-                {
-                    object.erase(it);
-                }
+                object.erase(it);
            }
        }
    }
@@ -1084,16 +1020,6 @@ class json_sax_dom_callback_parser

        JSON_ASSERT(object_element);
        *object_element = std::move(value);
-        if (!skip_callback)
-        {
-            // this scalar value finally, definitively replaces whatever was
-            // at this slot; drop any pending duplicate-key stash entry for
-            // it since it can no longer be restored (a container value at
-            // this slot is resolved later, in end_object()/end_array(),
-            // since skip_callback is true for the placeholder handling that
-            // happens here for those)
-            resolve_duplicate_key_stash(object_element, false);
-        }
        return {true, object_element};
    }

@@ -1113,12 +1039,6 @@ class json_sax_dom_callback_parser
    std::vector<string_t> container_key_stack {}; // NOLINT(readability-redundant-member-init)
    /// helper to hold the reference for the next object element
    BasicJsonType* object_element = nullptr;
-    /// stash of (slot pointer, previous value) for object members that
-    /// already existed when key() was called again for the same key
-    /// (duplicate keys); used to restore the previous value if the new
-    /// value is later rejected by the callback, instead of erasing the
-    /// member entirely
-    std::vector<std::pair<BasicJsonType*, BasicJsonType>> duplicate_key_stash {};
    /// whether a syntax error occurred
    bool errored = false;
    /// callback function
@@ -127,25 +127,6 @@ constexpr bool input_adapter_supports_seek(std::false_type /*detected*/)
    return false;
 }

-// Detect whether an input adapter reads with one character of lookahead that
-// can be left in the input (see input_stream_adapter::supports_lookahead,
-// which is only defined with JSON_PRECISE_STREAM_POSITION), detected like
-// supports_seek above.
-template<typename InputAdapterType>
-using detect_supports_lookahead = decltype(InputAdapterType::supports_lookahead);
-
-template<typename InputAdapterType>
-constexpr bool input_adapter_supports_lookahead(std::true_type /*detected*/)
-{
-    return InputAdapterType::supports_lookahead;
-}
-
-template<typename InputAdapterType>
-constexpr bool input_adapter_supports_lookahead(std::false_type /*detected*/)
-{
-    return false;
-}
-
 // Detect whether an input adapter exposes a contiguous byte block that the
 // lexer can scan directly (see iterator_input_adapter::supports_bulk_scan).
 // Adapters without the flag - file, stream, wide-string, user-defined - fall
@@ -186,12 +167,6 @@ class lexer : public lexer_base<BasicJsonType>
    static constexpr bool lazy_token_string =
        input_adapter_supports_seek<InputAdapterType>(is_detected<detect_supports_seek, InputAdapterType> {});

-    /// whether a simulated unget can be passed on to the input adapter, which
-    /// then leaves the character in the input; see
-    /// input_adapter_supports_lookahead
-    static constexpr bool can_release_lookahead =
-        input_adapter_supports_lookahead<InputAdapterType>(is_detected<detect_supports_lookahead, InputAdapterType> {});
-
    /// whether string scanning may bulk-consume runs of ordinary characters
    /// directly from a contiguous input buffer (SWAR fast path). This requires
    /// the token to be reconstructible lazily (lazy_token_string), so bypassing
@@ -977,9 +952,7 @@ class lexer : public lexer_base<BasicJsonType>
                        case '\n':
                        case '\r':
                        case char_traits<char_type>::eof():
-#if !JSON_STRICT_NUL_HANDLING
                        case '\0':
-#endif
                            return true;

                        default:
@@ -997,10 +970,8 @@ class lexer : public lexer_base<BasicJsonType>
                {
                    switch (get())
                    {
-#if !JSON_STRICT_NUL_HANDLING
-                        case '\0':
-#endif
                        case char_traits<char_type>::eof():
+                        case '\0':
                        {
                            error_message = "invalid comment; missing closing '*/'";
                            return false;
@@ -1923,21 +1894,6 @@ scan_number_done:
        uncapture_char(std::integral_constant<bool, lazy_token_string> {});
    }

-    /// adapter without lookahead: nothing to do (see release_lookahead)
-    void release_lookahead_impl(std::false_type /*can_release*/) const noexcept {}
-
-    /// adapter with lookahead: leave the character in the input instead
-    void release_lookahead_impl(std::true_type /*can_release*/)
-    {
-        if (next_unget)
-        {
-            // the character is read from the input again rather than replayed
-            // from current, so the adapter must not step over it
-            next_unget = false;
-            ia.release_lookahead();
-        }
-    }
-
    /// seekable adapter: nothing was captured, so nothing to undo
    void uncapture_char(std::true_type /*lazy*/) const noexcept {}

@@ -2001,31 +1957,6 @@ scan_number_done:
        return position;
    }

-    /*!
-    @brief pass a pending simulated unget on to the input
-
-    unget() only rewinds the lexer's own bookkeeping, so the character that
-    terminated the last token (e.g. the character after a number) would still
-    be stepped over when the input adapter is done. Callers that hand the
-    input back to the user afterwards - operator>> and non-strict sax_parse -
-    call this once when scanning is done, so that the input is positioned
-    right after the value.
-
-    Adapters without lookahead (see input_adapter_supports_lookahead) are not
-    handed back to the user, so this is a no-op for them. Without
-    JSON_PRECISE_STREAM_POSITION, no adapter has lookahead, so this is always a
-    no-op and the terminating character stays consumed.
-
-    Scanning may continue after this call: @a next_unget is cleared, and the
-    character is read from the input again instead of being replayed from
-    @a current. A pending unget of EOF needs no special case, because reaching
-    EOF leaves no lookahead to release.
-    */
-    void release_lookahead()
-    {
-        release_lookahead_impl(std::integral_constant<bool, can_release_lookahead> {});
-    }
-
 #if JSON_DIAGNOSTIC_POSITIONS
    /// return the offset of the first character of the last read token; unlike
    /// the token's parsed value, this accounts for escape sequences
@@ -2222,12 +2153,9 @@ scan_number_done:
            case '9':
                return scan_number_dispatch(std::integral_constant<bool, bulk_scan> {});

-#if !JSON_STRICT_NUL_HANDLING
+            // end of input (the null byte is needed when parsing from
+            // string literals)
            case '\0':
-#endif
-            // end of input; by default, a null byte is also treated as end of
-            // input for backwards compatibility (see JSON_STRICT_NUL_HANDLING
-            // to opt into rejecting a null byte in the input instead)
            case char_traits<char_type>::eof():
                return token_type::end_of_input;

@@ -100,22 +100,13 @@ class parser
            json_sax_dom_callback_parser<BasicJsonType, InputAdapterType> sdp(result, callback, allow_exceptions, &m_lexer);
            sax_parse_internal(&sdp);

-            if (strict)
+            // in strict mode, input must be completely read
+            if (strict && (get_token() != token_type::end_of_input))
            {
-                // in strict mode, input must be completely read
-                if (get_token() != token_type::end_of_input)
-                {
-                    sdp.parse_error(m_lexer.get_position(),
-                                    m_lexer.get_token_string(),
-                                    parse_error::create(101, m_lexer.get_position(),
-                                                        exception_message(token_type::end_of_input, "value"), nullptr));
-                }
-            }
-            else
-            {
-                // the caller keeps using the input: position it right after
-                // the value by leaving the character that terminated it
-                m_lexer.release_lookahead();
+                sdp.parse_error(m_lexer.get_position(),
+                                m_lexer.get_token_string(),
+                                parse_error::create(101, m_lexer.get_position(),
+                                                    exception_message(token_type::end_of_input, "value"), nullptr));
            }

            // in case of an error, return a discarded value
@@ -137,20 +128,12 @@ class parser
            json_sax_dom_parser<BasicJsonType, InputAdapterType> sdp(result, allow_exceptions, &m_lexer);
            sax_parse_internal(&sdp);

-            if (strict)
+            // in strict mode, input must be completely read
+            if (strict && (get_token() != token_type::end_of_input))
            {
-                // in strict mode, input must be completely read
-                if (get_token() != token_type::end_of_input)
-                {
-                    sdp.parse_error(m_lexer.get_position(),
-                                    m_lexer.get_token_string(),
-                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
-                }
-            }
-            else
-            {
-                // see above
-                m_lexer.release_lookahead();
+                sdp.parse_error(m_lexer.get_position(),
+                                m_lexer.get_token_string(),
+                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
            }

            // in case of an error, return a discarded value
@@ -183,24 +166,12 @@ class parser
        (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
        const bool result = sax_parse_internal(sax);

-        if (result)
+        // strict mode: next byte must be EOF
+        if (result && strict && (get_token() != token_type::end_of_input))
        {
-            if (strict)
-            {
-                // strict mode: next byte must be EOF
-                if (get_token() != token_type::end_of_input)
-                {
-                    return sax->parse_error(m_lexer.get_position(),
-                                            m_lexer.get_token_string(),
-                                            parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
-                }
-            }
-            else
-            {
-                // the caller keeps using the input: position it right after
-                // the value by leaving the character that terminated it
-                m_lexer.release_lookahead();
-            }
+            return sax->parse_error(m_lexer.get_position(),
+                                    m_lexer.get_token_string(),
+                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
        }

        return result;
@@ -88,13 +88,8 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci

    iter_impl() = default;
    ~iter_impl() = default;
-    // the exception specification is left to be computed rather than declared:
-    // an array or object type whose iterator is not nothrow move constructible
-    // (std::deque's is not before libstdc++ 11) would make a declared noexcept
-    // differ from the implicit one, which deletes the function -- and is an
-    // error outright with older compilers
-    iter_impl(iter_impl&&) = default; // NOLINT(hicpp-noexcept-move,performance-noexcept-move-constructor,cppcoreguidelines-noexcept-move-operations)
-    iter_impl& operator=(iter_impl&&) = default; // NOLINT(hicpp-noexcept-move,performance-noexcept-move-constructor,cppcoreguidelines-noexcept-move-operations)
+    iter_impl(iter_impl&&) noexcept = default;
+    iter_impl& operator=(iter_impl&&) noexcept = default;

    /*!
    @brief constructor for a given JSON instance
@@ -17,7 +17,6 @@
 #endif  // JSON_NO_IO
 #include <limits> // max
 #include <numeric> // accumulate
-#include <set> // set
 #include <string> // string
 #include <utility> // move
 #include <vector> // vector
@@ -72,7 +71,7 @@ class json_pointer
                               string_t{},
                               [](const string_t& a, const string_t& b)
        {
-            return detail::concat<string_t>(a, '/', detail::escape(b));
+            return detail::concat(a, '/', detail::escape(b));
        });
    }

@@ -266,7 +265,7 @@ class json_pointer
            JSON_THROW(detail::parse_error::create(109, 0, detail::concat("array index '", s, "' is not a number"), nullptr));
        }

-        const char* p = s.data();
+        const char* p = s.c_str();
        char* p_end = nullptr; // NOLINT(misc-const-correctness)
        errno = 0; // strtoull doesn't reset errno
        const unsigned long long res = std::strtoull(p, &p_end, 10); // NOLINT(runtime/int)
@@ -301,35 +300,19 @@ class json_pointer
    }

  private:
-    /*!
-    @brief the reference token sequences that denote arrays
-
-    @ref unflatten collects the pointer prefixes that have a reference token 0
-    among their children; @ref get_and_create creates arrays exactly below
-    those prefixes and objects everywhere else. Deciding this up front keeps
-    the result independent of the order in which the flattened object is
-    iterated, which is unspecified for some object types.
-    */
-    using array_parents_t = std::set<std::vector<string_t>>;
-
    /*!
    @brief create and return a reference to the pointed to value

    @complexity Linear in the number of reference tokens.

-    @throw parse_error.106 if an array index begins with '0'
    @throw parse_error.109 if array index is not a number
    @throw type_error.313 if value cannot be unflattened
    */
    template<typename BasicJsonType>
-    BasicJsonType& get_and_create(BasicJsonType& j, const array_parents_t& array_parents) const
+    BasicJsonType& get_and_create(BasicJsonType& j) const
    {
        auto* result = &j;

-        // the reference tokens that have been consumed so far; used to look up
-        // whether the value to be created below is an array or an object
-        std::vector<string_t> prefix;
-
        // in case no reference tokens exist, return a reference to the JSON value
        // j which will be overwritten by a primitive value
        for (const auto& reference_token : reference_tokens)
@@ -338,11 +321,10 @@ class json_pointer
            {
                case detail::value_t::null:
                {
-                    if (array_parents.find(prefix) != array_parents.end())
+                    if (reference_token == "0")
                    {
-                        // some reference token below this position is 0, so the
-                        // value is an array
-                        result = &result->operator[](array_index<BasicJsonType>(reference_token));
+                        // start a new array if the reference token is 0
+                        result = &result->operator[](0);
                    }
                    else
                    {
@@ -382,8 +364,6 @@ class json_pointer
                default:
                    JSON_THROW(detail::type_error::create(313, "invalid value to unflatten", &j));
            }
-
-            prefix.push_back(reference_token);
        }

        return *result;
@@ -857,8 +837,7 @@ class json_pointer
        {
            // use the text between the beginning of the reference token
            // (start) and the last slash (slash).
-            const auto count = (slash == string_t::npos ? reference_string.size() : slash) - start;
-            auto reference_token = string_t(reference_string.data() + start, count);
+            auto reference_token = reference_string.substr(start, slash - start);

            // check reference tokens are properly escaped
            for (std::size_t pos = reference_token.find_first_of('~');
@@ -974,24 +953,6 @@ class json_pointer

        BasicJsonType result;

-        // collect the pointer prefixes that have a reference token 0 among
-        // their children; the values below them are arrays, all others are
-        // objects (see array_parents_t)
-        array_parents_t array_parents;
-        for (const auto& element : *value.m_data.m_value.object)
-        {
-            json_pointer ptr(element.first);
-            std::vector<string_t> prefix;
-            for (auto& reference_token : ptr.reference_tokens)
-            {
-                if (reference_token == "0")
-                {
-                    array_parents.insert(prefix);
-                }
-                prefix.push_back(std::move(reference_token));
-            }
-        }
-
        // iterate the JSON object values
        for (const auto& element : *value.m_data.m_value.object)
        {
@@ -1004,7 +965,7 @@ class json_pointer
            // that if the JSON pointer is "" (i.e., points to the whole value),
            // function get_and_create returns a reference to the result itself.
            // An assignment will then create a primitive value.
-            json_pointer(element.first).get_and_create(result, array_parents) = element.second;
+            json_pointer(element.first).get_and_create(result) = element.second;
        }

        return result;
@@ -186,15 +186,6 @@
    #define JSON_NO_UNIQUE_ADDRESS
 #endif

-// Clang targeting MinGW does not survive the thread_local storage the copy
-// constructor uses to bound its descent: every test that copies a value
-// segfaults with clang 11.0.1 and clang 18.1.8, while the same tests pass with
-// GCC targeting MinGW and with every other toolchain the library is tested on.
-// Copying works the same way without the counter, only more slowly.
-#if !defined(JSON_NO_THREAD_LOCAL) && defined(__clang__) && defined(__MINGW32__)
-    #define JSON_NO_THREAD_LOCAL 1
-#endif
-
 // disable documentation warnings on clang
 #if defined(__clang__)
    #pragma clang diagnostic push
@@ -813,6 +804,6 @@ void templated_json_throw(ExceptionType exception)
    #define JSON_USE_GLOBAL_UDLS 1
 #endif

-#ifndef JSON_STRICT_NUL_HANDLING
-    #define JSON_STRICT_NUL_HANDLING 0
+#ifndef JSON_BRACE_INIT_COPY_SEMANTICS
+    #define JSON_BRACE_INIT_COPY_SEMANTICS 0
 #endif
@@ -26,7 +26,7 @@
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
 #undef JSON_USE_GLOBAL_UDLS
-#undef JSON_STRICT_NUL_HANDLING
+#undef JSON_BRACE_INIT_COPY_SEMANTICS

 #ifndef JSON_TEST_KEEP_MACROS
    #undef JSON_CATCH
@@ -44,8 +44,6 @@
    #undef JSON_HAS_STD_FORMAT
    #undef JSON_HAS_STATIC_RTTI
    #undef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
-    #undef JSON_BRACE_INIT_COPY_SEMANTICS
-    #undef JSON_PRECISE_STREAM_POSITION
 #endif

 #include <nlohmann/thirdparty/hedley/hedley_undef.hpp>
@@ -172,18 +172,17 @@ struct has_to_json < BasicJsonType, T, enable_if_t < !is_basic_json<T>::value >>
 template<typename T>
 using detect_key_compare = typename T::key_compare;

-// obtains the actual object key comparator: object_t::key_compare if the
-// object type defines it, and default_object_comparator_t otherwise
-//
-// note detected_or_t is used rather than std::conditional, because the latter
-// names both of its type arguments eagerly; object_t::key_compare would then
-// be a hard error for an object type that does not define it
+template<typename T>
+struct has_key_compare : std::integral_constant<bool, is_detected<detect_key_compare, T>::value> {};
+
+// obtains the actual object key comparator
 template<typename BasicJsonType>
 struct actual_object_comparator
 {
    using object_t = typename BasicJsonType::object_t;
    using object_comparator_t = typename BasicJsonType::default_object_comparator_t;
-    using type = detected_or_t<object_comparator_t, detect_key_compare, object_t>;
+    using type = typename std::conditional < has_key_compare<object_t>::value,
+          typename object_t::key_compare, object_comparator_t>::type;
 };

 template<typename BasicJsonType>
@@ -779,22 +778,6 @@ using has_erase_with_key_type = typename std::conditional <
                                std::true_type,
                                std::false_type >::type;

-template<typename ObjectType, typename IteratorType>
-using detect_erase_with_iterator = decltype(std::declval<ObjectType&>().erase(std::declval<IteratorType>()));
-
-// type trait to check if erase(iterator) returns void instead of the following
-// iterator, as the object types that do not compute a successor the caller may
-// not need do
-template<typename ObjectType, typename IteratorType>
-using erase_returns_void = is_detected_exact<void, detect_erase_with_iterator, ObjectType, IteratorType>;
-
-template<typename T>
-using detect_capacity = decltype(std::declval<const T&>().capacity());
-
-// type trait to check if a type has a capacity() member function
-template<typename T>
-struct has_capacity : std::integral_constant<bool, is_detected<detect_capacity, T>::value> {};
-
 // a naive helper to check if a type is an ordered_map (exploits the fact that
 // ordered_map inherits capacity() from std::vector)
 template <typename T>
@@ -13,7 +13,6 @@
 #include <iterator> // back_inserter
 #include <memory> // shared_ptr, make_shared
 #include <string> // basic_string
-#include <utility> // move
 #include <vector> // vector

 #ifndef JSON_NO_IO
@@ -45,32 +44,22 @@ template<typename CharType> struct output_adapter_protocol
 template<typename CharType>
 using output_adapter_t = std::shared_ptr<output_adapter_protocol<CharType>>;

-/// @brief non-virtual output sink writing into a std::vector
-///
-/// This sink is not part of the virtual output_adapter_protocol hierarchy: it is
-/// passed to binary_writer by value as a template parameter, so
-/// write_character()/write_characters() are ordinary (inlinable) calls with no
-/// vtable lookup and no shared_ptr. It is used for the common
-/// `to_cbor`/`to_msgpack`/... into a std::vector. output_vector_adapter below
-/// wraps this same sink to provide the virtual interface.
+/// output adapter for byte vectors
 template<typename CharType, typename AllocatorType = std::allocator<CharType>>
-class output_vector_sink
+class output_vector_adapter : public output_adapter_protocol<CharType>
 {
  public:
-    explicit output_vector_sink(std::vector<CharType, AllocatorType>& vec) noexcept
+    explicit output_vector_adapter(std::vector<CharType, AllocatorType>& vec) noexcept
        : v(vec)
    {}

-    void write_character(CharType c)
+    void write_character(CharType c) override
    {
        v.push_back(c);
    }

-    // no JSON_HEDLEY_NON_NULL here: binary_writer legitimately passes a null
-    // pointer with length 0 for empty strings/binary values. Appending an empty
-    // range is a no-op; the type-erased path tolerates this via the (unattributed)
-    // virtual base, and the concrete sink must do the same.
-    void write_characters(const CharType* s, std::size_t length)
+    JSON_HEDLEY_NON_NULL(2)
+    void write_characters(const CharType* s, std::size_t length) override
    {
        v.insert(v.end(), s, s + length);
    }
@@ -79,34 +68,6 @@ class output_vector_sink
    std::vector<CharType, AllocatorType>& v;
 };

-/// output adapter for byte vectors
-///
-/// The appending itself lives in output_vector_sink; this class only adds the
-/// virtual output_adapter_protocol interface on top of it, so both the
-/// type-erased and the templated path share one implementation.
-template<typename CharType, typename AllocatorType = std::allocator<CharType>>
-class output_vector_adapter : public output_adapter_protocol<CharType>
-{
-  public:
-    explicit output_vector_adapter(std::vector<CharType, AllocatorType>& vec) noexcept
-        : sink(vec)
-    {}
-
-    void write_character(CharType c) override
-    {
-        sink.write_character(c);
-    }
-
-    JSON_HEDLEY_NON_NULL(2)
-    void write_characters(const CharType* s, std::size_t length) override
-    {
-        sink.write_characters(s, length);
-    }
-
-  private:
-    output_vector_sink<CharType, AllocatorType> sink;
-};
-
 #ifndef JSON_NO_IO
 /// output adapter for output streams
 template<typename CharType>
@@ -157,39 +118,6 @@ class output_string_adapter : public output_adapter_protocol<CharType>
    StringType& str;
 };

-/// @brief output sink forwarding to a type-erased output adapter
-///
-/// Wraps the polymorphic output_adapter_t so the same binary_writer template can
-/// also target arbitrary adapters (output streams, strings, user-provided
-/// adapters) via the `output_adapter`-based overloads. Each write still goes
-/// through one virtual call, exactly as before; only the concrete sinks above
-/// avoid it.
-template<typename CharType>
-class output_adapter_sink
-{
-  public:
-    explicit output_adapter_sink(output_adapter_t<CharType> adapter)
-        : oa(std::move(adapter))
-    {
-        JSON_ASSERT(oa);
-    }
-
-    void write_character(CharType c)
-    {
-        oa->write_character(c);
-    }
-
-    // no JSON_HEDLEY_NON_NULL: forwards (null, 0) for empty payloads, exactly as
-    // the type-erased path already did before this sink existed
-    void write_characters(const CharType* s, std::size_t length)
-    {
-        oa->write_characters(s, length);
-    }
-
-  private:
-    output_adapter_t<CharType> oa;
-};
-
 template<typename CharType, typename StringType = std::basic_string<CharType>>
 class output_adapter
 {
@@ -30,8 +30,8 @@
 #include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/output/binary_writer.hpp>
 #include <nlohmann/detail/output/output_adapters.hpp>
-#include <nlohmann/detail/recursion_depth_limit.hpp>
 #include <nlohmann/detail/string_concat.hpp>
+#include <nlohmann/detail/string_utils.hpp>
 #include <nlohmann/detail/value_t.hpp>

 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -58,8 +58,6 @@ class serializer
    using number_integer_t = typename BasicJsonType::number_integer_t;
    using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
    using binary_char_t = typename BasicJsonType::binary_t::value_type;
-    static constexpr std::uint8_t UTF8_ACCEPT = 0;
-    static constexpr std::uint8_t UTF8_REJECT = 1;

  public:
    /*!
@@ -134,7 +132,7 @@ class serializer

    Serializing a container descends into its elements, so a value nested deeply
    enough used to exhaust the call stack and terminate the process with no
-    exception to catch. The descent is bounded here: once @ref recursion_depth_limit
+    exception to catch. The descent is bounded here: once @ref dump_depth_limit
    levels have been entered, @ref dump_iteratively writes out what is left
    without the call stack. A value nested less deeply than that - all but a
    vanishing minority - is written by exactly the code that always wrote it.
@@ -149,7 +147,7 @@ class serializer
        {
            case value_t::object:
            {
-                if (JSON_HEDLEY_UNLIKELY(depth >= recursion_depth_limit()))
+                if (JSON_HEDLEY_UNLIKELY(depth >= dump_depth_limit()))
                {
                    dump_iteratively(val, current_indent);
                    return;
@@ -224,7 +222,7 @@ class serializer

            case value_t::array:
            {
-                if (JSON_HEDLEY_UNLIKELY(depth >= recursion_depth_limit()))
+                if (JSON_HEDLEY_UNLIKELY(depth >= dump_depth_limit()))
                {
                    dump_iteratively(val, current_indent);
                    return;
@@ -409,12 +407,19 @@ class serializer
    }

  private:
+    /// the number of levels @ref dump_internal descends into before it hands
+    /// over to @ref dump_iteratively
+    static constexpr std::size_t dump_depth_limit()
+    {
+        return 128;
+    }
+
    /*!
    @brief write out @a val and everything below it without the call stack

    Emits the same bytes as @ref dump_internal, keeping the containers it has
    entered on an explicit stack instead of descending into them. Only reached
-    for values nested deeper than @ref recursion_depth_limit, which is why it is not
+    for values nested deeper than @ref dump_depth_limit, which is why it is not
    written for speed: walking every value this way measured up to 20% slower on
    object-heavy documents than letting the compiler drive the descent.
    */
@@ -1055,7 +1060,7 @@ class serializer
            {
                case error_handler_t::strict:
                {
-                    JSON_THROW(type_error::create(316, concat("incomplete UTF-8 string; last byte: 0x", hex_bytes(static_cast<std::uint8_t>(s[s.size() - 1] | 0))), nullptr));
+                    JSON_THROW(type_error::create(316, concat("incomplete UTF-8 string; last byte: 0x", hex_bytes(static_cast<std::uint8_t>(s.back() | 0))), nullptr));
                }

                case error_handler_t::ignore:
@@ -1316,19 +1321,6 @@ class serializer
        pos += 6;
    }

-    /*!
-    @brief convert a single element of a binary value to its byte value
-
-    The elements of a binary value are dumped as the numbers 0..255, regardless
-    of the value type of the configured BinaryType: that type may be signed
-    (`char`), unsigned (`std::uint8_t`), or not an integer at all
-    (`std::byte`), none of which @ref dump_integer can handle uniformly.
-    */
-    static std::uint8_t to_byte_value(binary_char_t x) noexcept
-    {
-        return static_cast<std::uint8_t>(x);
-    }
-
    // templates to avoid warnings about useless casts
    template <typename NumberType, enable_if_t<std::is_signed<NumberType>::value, int> = 0>
    bool is_negative_number(NumberType x)
@@ -1350,10 +1342,8 @@ class serializer
    an arbitrary number, and the three digits it takes at most are written
    straight into the write buffer.

-    Any byte type that is not a plain unsigned byte is converted to its
-    @ref to_byte_value "byte value" and left to @ref dump_integer, so a signed
-    or non-integral BinaryType::value_type (`char`, `std::byte`, ...) still
-    dumps as 0..255.
+    Any byte type that is not a plain unsigned byte is left to @ref dump_integer,
+    whose representation of it may differ.
    */
    template<typename ByteType>
    void dump_byte(const ByteType value)
@@ -1366,7 +1356,7 @@ class serializer
    template<typename ByteType>
    void dump_byte(const ByteType value, std::false_type /*is_plain_byte*/)
    {
-        dump_integer(to_byte_value(value));
+        dump_integer(value);
    }

    template<typename ByteType>
@@ -1412,7 +1402,8 @@ class serializer
    template < typename NumberType, detail::enable_if_t <
                   std::is_integral<NumberType>::value ||
                   std::is_same<NumberType, number_unsigned_t>::value ||
-                   std::is_same<NumberType, number_integer_t>::value,
+                   std::is_same<NumberType, number_integer_t>::value ||
+                   std::is_same<NumberType, binary_char_t>::value,
                   int > = 0 >
    void dump_integer(NumberType x)
    {
@@ -1592,62 +1583,6 @@ class serializer
        }
    }

-    /*!
-    @brief check whether a string is UTF-8 encoded
-
-    The function checks each byte of a string whether it is UTF-8 encoded. The
-    result of the check is stored in the @a state parameter. The function must
-    be called initially with state 0 (accept). State 1 means the string must
-    be rejected, because the current byte is not allowed. If the string is
-    completely processed, but the state is non-zero, the string ended
-    prematurely; that is, the last byte indicated more bytes should have
-    followed.
-
-    @param[in,out] state  the state of the decoding
-    @param[in,out] codep  codepoint (valid only if resulting state is UTF8_ACCEPT)
-    @param[in] byte       next byte to decode
-    @return               new state
-
-    @note The function has been edited: a std::array is used.
-
-    @copyright Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de>
-    @sa http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
-    */
-    static std::uint8_t decode(std::uint8_t& state, std::uint32_t& codep, const std::uint8_t byte) noexcept
-    {
-        static const std::array<std::uint8_t, 400> utf8d =
-        {
-            {
-                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 00..1F
-                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20..3F
-                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 40..5F
-                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 60..7F
-                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // 80..9F
-                7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // A0..BF
-                8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // C0..DF
-                0xA, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x4, 0x3, 0x3, // E0..EF
-                0xB, 0x6, 0x6, 0x6, 0x5, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, // F0..FF
-                0x0, 0x1, 0x2, 0x3, 0x5, 0x8, 0x7, 0x1, 0x1, 0x1, 0x4, 0x6, 0x1, 0x1, 0x1, 0x1, // s0..s0
-                1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, // s1..s2
-                1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, // s3..s4
-                1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, // s5..s6
-                1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 // s7..s8
-            }
-        };
-
-        JSON_ASSERT(static_cast<std::size_t>(byte) < utf8d.size());
-        const std::uint8_t type = utf8d[byte];
-
-        codep = (state != UTF8_ACCEPT)
-                ? (byte & 0x3fu) | (codep << 6u)
-                : (0xFFu >> type) & (byte);
-
-        const std::size_t index = 256u + (static_cast<size_t>(state) * 16u) + static_cast<size_t>(type);
-        JSON_ASSERT(index < utf8d.size());
-        state = utf8d[index];
-        return state;
-    }
-
    /*
     * Overload to make the compiler happy while it is instantiating
     * dump_integer for number_unsigned_t.
@@ -1,35 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#pragma once
-
-#include <cstddef> // size_t
-
-#include <nlohmann/detail/abi_macros.hpp>
-
-NLOHMANN_JSON_NAMESPACE_BEGIN
-namespace detail
-{
-
-/*!
-@brief the number of nesting levels an operation recurses into
-
-Operations that walk a value (serializing, hashing, merging, ...) recurse once
-per nesting level, which is fastest, but a value nested deeply enough would
-exhaust the call stack. So they recurse only this many levels deep and finish
-whatever lies below with an explicit stack. All of them share this limit.
-
-@sa https://github.com/nlohmann/json/issues/5387
-*/
-constexpr std::size_t recursion_depth_limit() noexcept
-{
-    return 128;
-}
-
-}  // namespace detail
-NLOHMANN_JSON_NAMESPACE_END
@@ -8,56 +8,50 @@

 #pragma once

-#include <cstddef> // size_t
-
 #include <nlohmann/detail/abi_macros.hpp>

 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {

+/*!
+@brief replace all occurrences of a substring by another string
+
+@param[in,out] s  the string to manipulate; changed so that all
+               occurrences of @a f are replaced with @a t
+@param[in]     f  the substring to replace with @a t
+@param[in]     t  the string to replace @a f
+
+@pre The search string @a f must not be empty. **This precondition is
+enforced with an assertion.**
+
+@since version 2.0.0
+*/
+template<typename StringType>
+inline void replace_substring(StringType& s, const StringType& f,
+                              const StringType& t)
+{
+    JSON_ASSERT(!f.empty());
+    for (auto pos = s.find(f);                // find the first occurrence of f
+            pos != StringType::npos;          // make sure f was found
+            s.replace(pos, f.size(), t),      // replace with t, and
+            pos = s.find(f, pos + t.size()))  // find the next occurrence of f
+    {}
+}
+
 /*!
 * @brief string escaping as described in RFC 6901 (Sect. 4)
 * @param[in] s string to escape
 * @return    escaped string
 *
 * Note the order of escaping "~" to "~0" and "/" to "~1" is important.
- *
- * The string is rebuilt in a single pass, appending whole runs between the
- * characters that need escaping. Scanning with find_first_of() keeps the
- * common case -- nothing to escape -- as fast as a single search, while
- * repeated replace() calls would move the tail of the string once per
- * escaped character.
 */
 template<typename StringType>
-inline StringType escape(const StringType& s)
+inline StringType escape(StringType s)
 {
-    auto next_special = [&s](std::size_t from)
-    {
-        const auto tilde = s.find_first_of('~', from);
-        const auto slash = s.find_first_of('/', from);
-        return tilde < slash ? tilde : slash; // npos is the largest value
-    };
-
-    auto pos = next_special(0);
-    if (pos == StringType::npos)
-    {
-        return s;
-    }
-
-    StringType result;
-    result.reserve(s.size() + 2);
-
-    std::size_t run = 0;
-    while (pos != StringType::npos)
-    {
-        result.append(s.data() + run, pos - run);
-        result.append(s[pos] == '~' ? "~0" : "~1", 2);
-        run = pos + 1;
-        pos = next_special(run);
-    }
-    result.append(s.data() + run, s.size() - run);
-    return result;
+    replace_substring(s, StringType{"~"}, StringType{"~0"});
+    replace_substring(s, StringType{"/"}, StringType{"~1"});
+    return s;
 }

 /*!
@@ -66,43 +60,12 @@ inline StringType escape(const StringType& s)
 * @return    unescaped string
 *
 * Note the order of escaping "~1" to "/" and "~0" to "~" is important.
- *
- * Rebuilt in a single pass, see @ref escape. A "~" that is followed by
- * neither "0" nor "1" is passed through unchanged; @ref json_pointer rejects
- * such input before it gets here.
 */
 template<typename StringType>
 inline void unescape(StringType& s)
 {
-    auto pos = s.find_first_of('~', 0);
-    if (pos == StringType::npos)
-    {
-        return;
-    }
-
-    StringType result;
-    result.reserve(s.size());
-
-    std::size_t run = 0;
-    while (pos != StringType::npos)
-    {
-        result.append(s.data() + run, pos - run);
-
-        const auto next = pos + 1;
-        if (next < s.size() && (s[next] == '0' || s[next] == '1'))
-        {
-            result.append(s[next] == '0' ? "~" : "/", 1);
-            run = pos + 2;
-        }
-        else
-        {
-            result.append("~", 1);
-            run = pos + 1;
-        }
-        pos = s.find_first_of('~', run);
-    }
-    result.append(s.data() + run, s.size() - run);
-    s = result;
+    replace_substring(s, StringType{"~1"}, StringType{"/"});
+    replace_substring(s, StringType{"~0"}, StringType{"~"});
 }

 }  // namespace detail
@@ -8,10 +8,13 @@

 #pragma once

+#include <array> // array
 #include <cstddef> // size_t
+#include <cstdint> // uint8_t, uint32_t
 #include <string> // string, to_string

 #include <nlohmann/detail/abi_macros.hpp>
+#include <nlohmann/detail/macro_scope.hpp>

 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -33,5 +36,102 @@ StringType to_string(std::size_t value)
    return result;
 }

+///////////////////
+// UTF-8 decoding //
+///////////////////
+
+// UTF-8 decoder states used by decode() below
+static constexpr std::uint8_t UTF8_ACCEPT = 0;
+static constexpr std::uint8_t UTF8_REJECT = 1;
+
+/*!
+@brief process a byte of a UTF-8 sequence
+
+This is a single-byte step of a "shift-based" UTF-8 decoder originally
+written by Björn Hoehrmann. See
+http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.
+
+This decoder is the single source of truth for UTF-8 validation in this
+library: it is used both by the serializer (to escape and, in strict mode,
+reject ill-formed UTF-8 when dumping a string) and by the binary readers
+(to reject ill-formed UTF-8 in CBOR/MessagePack/BSON/UBJSON text strings at
+decode time; see @ref is_valid_utf8 below).
+
+@param[in,out] state  the current decoder state
+@param[in,out] codep  codepoint (valid only if resulting state is UTF8_ACCEPT)
+@param[in] byte       next byte to decode
+@return               new state
+
+@note Original source: http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
+@sa http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
+*/
+inline std::uint8_t decode(std::uint8_t& state, std::uint32_t& codep, const std::uint8_t byte) noexcept
+{
+    static const std::array<std::uint8_t, 400> utf8d =
+    {
+        {
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 00..1F
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20..3F
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 40..5F
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 60..7F
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // 80..9F
+            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // A0..BF
+            8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // C0..DF
+            0xA, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x4, 0x3, 0x3, // E0..EF
+            0xB, 0x6, 0x6, 0x6, 0x5, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, // F0..FF
+            0x0, 0x1, 0x2, 0x3, 0x5, 0x8, 0x7, 0x1, 0x1, 0x1, 0x4, 0x6, 0x1, 0x1, 0x1, 0x1, // s0..s0
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, // s1..s2
+            1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, // s3..s4
+            1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, // s5..s6
+            1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 // s7..s8
+        }
+    };
+
+    JSON_ASSERT(static_cast<std::size_t>(byte) < utf8d.size());
+    const std::uint8_t type = utf8d[byte];
+
+    codep = (state != UTF8_ACCEPT)
+            ? (byte & 0x3fu) | (codep << 6u)
+            : (0xFFu >> type) & (byte);
+
+    const std::size_t index = 256u + (static_cast<std::size_t>(state) * 16u) + static_cast<std::size_t>(type);
+    JSON_ASSERT(index < utf8d.size());
+    state = utf8d[index];
+    return state;
+}
+
+/*!
+@brief check whether a string consists solely of valid UTF-8
+
+Used by the CBOR/MessagePack/BSON/UBJSON binary readers to reject text
+strings that are not valid UTF-8 at decode time (RFC 8949 §3.1 and the
+MessagePack/BSON specifications all require text strings to be UTF-8), so
+that malformed input is caught immediately instead of only surfacing later
+as a type_error.316 when the resulting value is dumped.
+
+@param[in] s      the string to check
+@param[in] first  index of the first byte to check; the bytes before it are
+                  assumed to have been validated already and to end on a
+                  code point boundary
+@return whether @a s (from index @a first on) is valid UTF-8
+*/
+template<typename StringType>
+inline bool is_valid_utf8(const StringType& s, const std::size_t first = 0) noexcept
+{
+    std::uint8_t state = UTF8_ACCEPT;
+    std::uint32_t codepoint = 0;
+
+    for (std::size_t i = first; i < s.size(); ++i)
+    {
+        decode(state, codepoint, static_cast<std::uint8_t>(s[i]));
+        if (state == UTF8_REJECT)
+        {
+            return false;
+        }
+    }
+
+    return state == UTF8_ACCEPT;
+}
+
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
--- a/Show More
+++ b/Show More
Author	SHA1	Message	Date
Niels Lohmann	93c0a34171	⚡ validate only newly read bytes of binary-format strings get_string() validated the whole result after each call, but get_bytes() appends to it and CBOR indefinite-length strings collect all chunks in the same result, so every chunk re-validated everything read before it. An input of many small chunks took quadratic time (80000 one-byte chunks, 160 KB of input, took about 7 seconds). Only the newly read bytes are validated now, which also matches RFC 8949's requirement that every chunk is valid UTF-8 on its own. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-23 20:42:27 +02:00
Niels LohmannandClaude Sonnet 5	2d535eb96c	🐛 reject ill-formed UTF-8 in CBOR/MessagePack/BSON text strings at decode time (#5531 ) from_cbor()/from_msgpack()/from_bson() copied the raw bytes of a decoded text string into the resulting json value without any UTF-8 validation, even though RFC 8949 §3.1 (CBOR) and the MessagePack/BSON specifications all require text strings to be valid UTF-8. Malformed input only failed later, if the value was dump()'d, with a type_error.316 - so the allow_exceptions=false pattern used specifically to get a discarded sentinel instead of an exception did not discard this category of malformed input, unlike every other kind of malformed binary input this library rejects at decode time (see #5529). Fix this at the single choke point shared by BSON/CBOR/MessagePack/UBJSON string reads, binary_reader::get_string(): validate the bytes with the UTF-8 DFA right after they are read, and report failures the same way as every other binary_reader error (parse_error.113), so allow_exceptions and strict discarding behave consistently. get_binary()/binary blob reads are untouched and still accept arbitrary bytes, since only text strings are required to be UTF-8. There were two independent implementations of a UTF-8 validator: the lexer's streaming scanner, and the serializer's Hoehrmann DFA used by dump_escaped_impl(). Rather than write a third, the serializer's decode() function, its utf8d table and the UTF8_ACCEPT/UTF8_REJECT constants are extracted into detail/string_utils.hpp (a low-level header already included before both detail/input/ and detail/output/), alongside a new is_valid_utf8() helper built on the same decode() step. serializer.hpp's dump_escaped_impl() now calls the shared decode(), so there is exactly one UTF-8 validator in the codebase; dump()'s exact type_error.316 messages and byte-index reporting are unchanged (see the added regression-guard test in unit-serialization.cpp). Claude-Session: https://claude.ai/code/session_01N4RQ1Ahan5YAGbnAQGjZTY Signed-off-by: Niels Lohmann <mail@nlohmann.me> Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>	2026-09-23 20:42:25 +02:00
Niels Lohmann	0886b7fe7e	🐛 fix BSON conformance issue Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-14 21:22:01 +02:00
Niels Lohmann	0e1ae592af	🐛 fix BSON conformance issue Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-14 21:22:00 +02:00