Look up the key only once in the callback parser's key()

Since #5466, key() searched the object for a duplicate key and then looked the key up again to insert the placeholder. Use a single emplace() instead. Parsing a 32k-member object with a callback: 10.4 ms -> 7.2 ms (3.12.0: 8.0 ms). Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Clarify that double is only the default floating-point type in the docs (#5830 )
2026-10-14 18:27:13 +00:00 · 2026-10-14 20:20:59 +02:00 · 2026-10-14 18:28:49 +02:00 · 2026-10-14 17:40:55 +02:00 · 2026-10-14 17:40:21 +02:00 · 2026-10-14 17:40:07 +02:00
180 changed files with 11279 additions and 3856 deletions
@@ -0,0 +1,3 @@
+# generated files are collapsed in diffs and excluded from language statistics
+single_include/** linguist-generated
+nlohmann_json.natvis linguist-generated
@@ -1,5 +1,5 @@
 # JSON for Modern C++ was originally written by Niels Lohmann.
-# Since 2013, over 250 contributors have helped to improve the library.
+# Since 2013, over 400 contributors have helped to improve the library.
 # This CODEOWNERS file is only to make sure that @nlohmann is requested
 # for a code review in case of a pull request.

@@ -98,7 +98,7 @@ $ ctest --test-dir build -j 10
 The test suite should report:

 ```
-100% tests passed, 0 tests failed out of 98
+100% tests passed, 0 tests failed out of <number of tests>
 ```

 #### Add tests
@@ -149,14 +149,17 @@ make build -C docs/mkdocs          # strict build: fails on broken links, anchor
 make check_mermaid -C docs/mkdocs  # checks the Mermaid diagrams (requires Node.js)
 ```

-A new API page also needs an entry in [`docs/docset/docSet.sql`](https://github.com/nlohmann/json/blob/develop/docs/docset/docSet.sql),
-the search index of the docset; `make build` reports missing entries.
+The search index of the docset is generated from [`mkdocs.yml`](https://github.com/nlohmann/json/blob/develop/docs/mkdocs/mkdocs.yml)
+and each page's title (H1) and declaration by
+[`docs/docset/generate_docset.py`](https://github.com/nlohmann/json/blob/develop/docs/docset/generate_docset.py);
+`make build` reports API pages that cannot be classified.

 ### Amalgamate the source code

 The single-header files
-[`single_include/nlohmann/json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp) and
-[`single_include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_fwd.hpp)
+[`single_include/nlohmann/json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp),
+[`single_include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_fwd.hpp), and
+[`single_include/nlohmann/json_literals.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_literals.hpp)
 are **generated** from the source files in the
 [`include/nlohmann` directory](https://github.com/nlohmann/json/tree/develop/include/nlohmann). **Do not** edit the
 files directly; instead, modify the include/nlohmann sources and regenerate the files by executing:
@@ -179,7 +182,7 @@ The amalgamation check in CI fails if any of these generated files is out of dat

 ## Recommended documentation

- The library’s [README file](https://github.com/nlohmann/json/blob/master/README.md) is an excellent starting point to
+- The library’s [README file](https://github.com/nlohmann/json/blob/develop/README.md) is an excellent starting point to
  understand its functionality.
 - The [documentation page](https://json.nlohmann.me) is the reference documentation of the library.
 - [RFC 8259](https://datatracker.ietf.org/doc/html/rfc8259) is the reference for the JavaScript Object Notation (JSON)
@@ -218,9 +221,9 @@ feature macros then allows users to test their code against the library in the n
 ### Break C++11 language conformance

 This library is designed to work with C++11 and later. This means that any
-[supported C++11 compiler](https://github.com/nlohmann/json/blob/master/README.md#supported-compilers) should compile
+[supported C++11 compiler](https://github.com/nlohmann/json/blob/develop/README.md#supported-compilers) should compile
 the library without problems. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual
-Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support.
+C++ 2013 and earlier are known not to work due to missing or incomplete C++11 support.

 Please do not add features that do not work with the mentioned supported compilers. Please guard features from C++14 and
 later against the respective [`JSON_HAS_CPP_14`](https://json.nlohmann.me/api/macros/json_has_cpp_11/) macros.
@@ -236,12 +239,11 @@ extension.
 The following areas really need contribution and are always welcomed:

 - Extending the **continuous integration** toward more exotic compilers such as Android NDK, Intel's Compiler, or the
-  bleeding-edge versions Clang.
- Improving the efficiency of the **JSON parser**. The current parser is implemented as a naive recursive descent parser
-  with hand-coded string handling. More sophisticated approaches like LALR parsers would be really appreciated. That
-  said, parser generators like Bison or ANTLR do not play nice with single-header files -- I really would like to keep
-  the parser inside the `json.hpp` header, and I am not aware of approaches similar to [`re2c`](http://re2c.org) for
-  parsing.
+  bleeding-edge versions of Clang.
+- Improving the efficiency of the **JSON parser**. The current parser is a hand-written iterative parser that keeps an
+  explicit stack instead of recursing, with hand-coded string handling. Speeding up the lexer or the value construction
+  would be appreciated. Parser generators like Bison or ANTLR do not play nice with single-header files -- I really
+  would like to keep the parser inside the `json.hpp` header.
 - Extending and updating existing **benchmarks** to include (the most recent version of) this library. Though efficiency
  is not everything, speed and memory consumption are very important characteristics for C++ developers, so having
  proper comparisons would be interesting.
@@ -52,7 +52,7 @@ body:
        If possible, provide a small and self-contained example that triggers
        the bug. Please understand that we cannot analyze and debug large code
        bases. Please do not paste screenshots here.
-      render: Shell
+      render: cpp
  - type: textarea
    id: output
    attributes:
@@ -79,7 +79,7 @@ body:
      description: >
        Which version of the library did you use? If it is a released version,
        please enter the version number (e.g., 3.12.0). Otherwise, please enter
-        the commit hash. If you got the library from another source as the
+        the commit hash. If you got the library from another source than the
        GitHub repository (e.g., via a package manager), please also state
        this.
    validations:
@@ -21,6 +21,17 @@ labels:
  files:
    - "cmake/.*"

+# other build systems
+- label: "CMake"
+  files:
+    - "(meson\\.build|meson_options\\.txt|BUILD\\.bazel|MODULE\\.bazel|Package\\.swift)"
+
+- label: "documentation"
+  files:
+    - ".github/ISSUE_TEMPLATE/.*"
+    - ".github/config\\.yml"
+    - ".github/(CONTRIBUTING|SECURITY|CODE_OF_CONDUCT|PULL_REQUEST_TEMPLATE)\\.md"
+
 - label: "CI"
  files:
    - ".github/workflows/.*"
@@ -28,7 +28,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -22,7 +22,7 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -46,7 +46,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -83,8 +83,7 @@ jobs:
          # byte for byte), so there is nothing to gain from checking out a
          # separate copy, and doing so would make this step fail on a PR
          # that adds support for a new dispatch table until that PR itself
-          # merges to develop, the same way generate_natvis.py's --version
-          # requirement briefly did.
+          # merges to develop.
          TMPDIR=$(mktemp -d ./macro_builder_check.XXXXXX)
          c++ -std=c++11 tools/macro_builder/main.cpp -o "$TMPDIR/macro_builder"
          "$TMPDIR/macro_builder" > "$TMPDIR/paste.hpp"
@@ -117,7 +116,6 @@ jobs:

          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 .
-          cp include/nlohmann/json_literals.hpp $INCLUDE_DIR/json_literals.hpp

          # the header list of the Bazel "json" target must match the files in include/
          cmake -P cmake/scripts/gen_bazel_build_file.cmake
@@ -138,17 +136,13 @@ jobs:
          ${{ github.workspace }}/venv/bin/astyle --project=tools/astyle/.astylerc --suffix=none --quiet \
            $(find $SOURCE_DIRS -type f \( -name '*.hpp' -o -name '*.cpp' -o -name '*.cu' \) -not -path 'tests/thirdparty/*' -not -path 'tests/abi/include/nlohmann/*' | sort)

+          # json_literals.hpp is copied verbatim from the (now formatted) include/
+          # directory, like `make amalgamate` does
+          cp include/nlohmann/json_literals.hpp $INCLUDE_DIR/json_literals.hpp
+
      - name: Regenerate nlohmann_json.natvis
        run: |
          cd $MAIN_DIR
-          # Pass --version explicitly so this step also works with the tool
-          # copy from develop before this repository's own generate_natvis.py
-          # learns to derive the version itself: the older script requires
-          # --version, and the newer one accepts it as an explicit override.
-          ABI_MACROS=include/nlohmann/detail/abi_macros.hpp
-          VERSION_MAJOR=$(grep -m1 'define NLOHMANN_JSON_VERSION_MAJOR' $ABI_MACROS | grep -o '[0-9]\+')
-          VERSION_MINOR=$(grep -m1 'define NLOHMANN_JSON_VERSION_MINOR' $ABI_MACROS | grep -o '[0-9]\+')
-          VERSION_PATCH=$(grep -m1 'define NLOHMANN_JSON_VERSION_PATCH' $ABI_MACROS | grep -o '[0-9]\+')
          # The template is what this check verifies the committed natvis
          # file against, so take it from this PR rather than from the
          # develop checkout: generate_natvis.py loads the template from its
@@ -156,7 +150,7 @@ jobs:
          # template could never pass. Like the macro_builder step above,
          # this only renders PR content in a job without credentials.
          cp tools/generate_natvis/nlohmann_json.natvis.j2 $NATVIS_TOOL_DIR/
-          python3 $NATVIS_TOOL_DIR/generate_natvis.py --version "$VERSION_MAJOR.$VERSION_MINOR.$VERSION_PATCH" $MAIN_DIR
+          python3 $NATVIS_TOOL_DIR/generate_natvis.py $MAIN_DIR

      - name: Build patch and check for differences
        id: diff
@@ -165,7 +159,7 @@ 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, or BUILD.bazel, nlohmann_json.natvis, or the macro_builder tables in macro_scope.hpp are out of date ('make amalgamate BUILD.bazel natvis' fixes all but the tables, see tools/macro_builder/README.md). Diff:"
            cat ${{ github.workspace }}/patch/amalgamation.patch
            echo "has_diff=true" >> "$GITHUB_OUTPUT"
          else
@@ -20,7 +20,7 @@ jobs:
    timeout-minutes: 30
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -13,7 +13,7 @@ jobs:
    runs-on: ubuntu-22.04
    steps:
    - name: Harden Runner
-      uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+      uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
      with:
        egress-policy: audit

@@ -27,7 +27,7 @@ jobs:

    steps:
    - name: Harden Runner
-      uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+      uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
      with:
        egress-policy: audit

@@ -20,7 +20,7 @@ jobs:
      pull-requests: write
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -96,7 +96,7 @@ 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, or `BUILD.bazel`, `nlohmann_json.natvis`, or the macro_builder tables in `macro_scope.hpp` are out of date. `make amalgamate BUILD.bazel natvis` fixes all but the tables (see `tools/macro_builder/README.md`).'
                    + (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'
@@ -21,7 +21,7 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -31,7 +31,7 @@ jobs:
      security-events: write
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -23,7 +23,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -15,6 +15,7 @@ on:
      - .github/SECURITY.md
      - cmake/clang_flags.cmake
      - cmake/gcc_flags.cmake
+      - include/nlohmann/detail/abi_macros.hpp
      - tests/fmt_formatter/project/main.cpp
      - tools/astyle/.astylerc
  workflow_dispatch:
@@ -36,7 +37,7 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -40,7 +40,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -36,7 +36,7 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -16,7 +16,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -80,7 +80,7 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -109,14 +109,15 @@ jobs:
    runs-on: ubuntu-latest
    strategy:
      matrix:
-        target: [ci_test_amalgamation, ci_test_single_header, ci_cppcheck, ci_cpplint, ci_reproducible_tests, ci_non_git_tests, ci_offline_testdata, ci_reuse_compliance, ci_test_valgrind]
+        target: [ci_test_single_header, ci_cppcheck, ci_cpplint, ci_reproducible_tests, ci_non_git_tests, ci_offline_testdata, ci_reuse_compliance, ci_test_valgrind]
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

      - name: Install Valgrind
+        if: matrix.target == 'ci_test_valgrind'
        run: sudo apt-get update ; sudo apt-get install -y valgrind
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
        with:
@@ -177,7 +178,7 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -279,7 +280,7 @@ jobs:
          persist-credentials: false
      - name: Get latest CMake and ninja
        uses: lukka/get-cmake@fffaaafeea488556c2c12dad60690008bc1caacb # v4.4.2
-      - name: Set env FORCE_STDCPPFS_FLAG for clang 7 / 8 / 9 / 10
+      - name: Disable filesystem support (std::filesystem is unusable) for clang 7 / 8 / 9 / 10
        run: echo "JSON_FORCED_GLOBAL_COMPILE_OPTIONS=-DJSON_HAS_FILESYSTEM=0;-DJSON_HAS_EXPERIMENTAL_FILESYSTEM=0" >> "$GITHUB_ENV"
        if: ${{ matrix.compiler == '7' || matrix.compiler == '8' || matrix.compiler == '9' || matrix.compiler == '10' }}
      - name: Run CMake
@@ -432,7 +433,7 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -455,7 +456,7 @@ jobs:
        target: [ci_test_examples, ci_test_build_documentation, ci_test_documentation_mermaid]
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@e14015d583714f6e62063499dc959a02595150a1 # v2.21.1
+        uses: step-security/harden-runner@351661ca32ac09a36dc5ee2d536e3128f2a3c8ed # v2.22.0
        with:
          egress-policy: audit

@@ -187,7 +187,7 @@ jobs:
      - name: Test
        run: cd build ; ctest -j 10 -C Debug --output-on-failure

-  clang-cl-12:
+  clang-cl:
    runs-on: windows-2022
    strategy:
      matrix:
@@ -217,8 +217,10 @@ jobs:
        uses: lukka/get-cmake@fffaaafeea488556c2c12dad60690008bc1caacb # v4.4.2
        with:
          cmakeVersion: 4.3.4
+      # CMAKE_CXX_FLAGS replaces CMake's MSVC defaults (which include /EHsc), and
+      # ci_module_cpp20 forwards it to the module build, so list /EHsc explicitly
      - name: Run CMake (Debug)
-        run: cmake -S . -B build -G "Visual Studio 17 2022" -DJSON_CI=ON -DCMAKE_CXX_FLAGS="/permissive- /std:c++latest /utf-8 /W4 /WX"
+        run: cmake -S . -B build -G "Visual Studio 17 2022" -DJSON_CI=ON -DCMAKE_CXX_FLAGS="/permissive- /std:c++latest /utf-8 /EHsc /W4 /WX"
      - name: Build
        run: cmake --build build --config Debug --target ci_module_cpp20
        
@@ -27,7 +27,6 @@
 /docs/docset/JSON_for_Modern_C++.tgz
 /docs/docset/docSet.dsidx
 /docs/mkdocs/.cache/
-/docs/mkdocs/docs/__pycache__/
 /docs/mkdocs/hooks/__pycache__/
 /docs/mkdocs/scripts/mermaid/node_modules/
 /docs/mkdocs/site/
@@ -47,3 +46,17 @@ nlohmann_json.spdx

 # Bazel-related
 MODULE.bazel.lock
+
+# backups left by `make check-amalgamation` or the ci_test_amalgamation target if they are interrupted
+/BUILD.bazel~
+/nlohmann_json.natvis~
+/single_include/nlohmann/*.hpp~
+/venv_astyle/
+
+# release outputs of `make release`
+/include.zip
+/include.zip.asc
+/json.tar.xz
+/json.tar.xz.asc
+/release_files/
+/single_include/nlohmann/*.asc
@@ -25,6 +25,7 @@ cc_library(
        "include/nlohmann/detail/conversions/from_json.hpp",
        "include/nlohmann/detail/conversions/to_chars.hpp",
        "include/nlohmann/detail/conversions/to_json.hpp",
+        "include/nlohmann/detail/conversions/zmij.hpp",
        "include/nlohmann/detail/exceptions.hpp",
        "include/nlohmann/detail/hash.hpp",
        "include/nlohmann/detail/input/binary_reader.hpp",
@@ -81,6 +82,7 @@ cc_library(
    hdrs = [
        "single_include/nlohmann/json.hpp",
        "single_include/nlohmann/json_fwd.hpp",
+        "single_include/nlohmann/json_literals.hpp",
    ],
    includes = ["single_include"],
    visibility = ["//visibility:public"],
@@ -8,7 +8,7 @@ authors:
    website: https://nlohmann.me
 title: "JSON for Modern C++"
 version: 3.12.0
-date-released: 2025-04-07
+date-released: 2025-04-11
 license: MIT
 repository-code: "https://github.com/nlohmann/json"
 url: https://json.nlohmann.me
@@ -30,7 +30,7 @@ endif ()
 option(NLOHMANN_JSON_BUILD_MODULES "Build C++ modules support" OFF)

 if(NLOHMANN_JSON_BUILD_MODULES)
-    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.28)
+    if(NOT CMAKE_VERSION VERSION_LESS 3.28)
        message(STATUS "Building nlohmann.json C++ module")
        add_subdirectory(src/modules)
    else()
@@ -14,7 +14,7 @@ This file describes the source for supporting files; that is, files that are not
 The [GitHub Actions](https://docs.github.com/en/actions) workflows that build, test, and analyze the library. Each file in this folder defines one workflow:

 - `ubuntu.yml`, `macos.yml`, `windows.yml` — build and run the test suite on Linux, macOS, and Windows.
- `check_amalgamation.yml` — verify that the single-header amalgamation in `single_include` is up to date on pull requests.
+- `check_amalgamation.yml` — verify on pull requests and pushes to `develop` that the generated files (the single-header amalgamation in `single_include`, `BUILD.bazel`, and `nlohmann_json.natvis`) are up to date.
 - `comment_check_amalgamation.yml` — comment on a pull request when the amalgamation check failed.
 - `cifuzz.yml` — run short fuzzing sessions via [OSS-Fuzz CIFuzz](https://google.github.io/oss-fuzz/getting-started/continuous-integration/) on pull requests.
 - `codeql-analysis.yml` — run [CodeQL](https://codeql.github.com) code scanning.
@@ -24,7 +24,9 @@ The [GitHub Actions](https://docs.github.com/en/actions) workflows that build, t
 - `dependency-review.yml` — scan dependency changes in pull requests for known vulnerabilities.
 - `labeler.yml` — the "Pull Request Labeler" workflow (see `.github/labeler.yml`).
 - `stale.yml` — comment on and close stale issues and pull requests.
- `publish_documentation.yml` — build and publish the documentation on every merge to the `develop` branch.
+- `publish_documentation.yml` — build and publish the documentation on pushes to the `develop` branch that touch the documentation sources (or the files it embeds).
+- `check_docs_links.yml` — check the links of the documentation weekly, as external links can break without any change in this repository.
+- `cancel_closed_pr_runs.yml` — cancel unfinished workflow runs of a pull request once it is closed or merged.

 Further documentation:

@@ -266,8 +268,9 @@ meson setup builddir
 ninja -C builddir
 ```

-`meson_options.txt` defines the options, which mirror the CMake options that change the library's target (for example,
-`-DDiagnostics=true`). Meson requires this file next to `meson.build`, so it is also part of `include.zip`. `make check_build_options`
+`meson_options.txt` defines the options, which mirror the names of the CMake options that change the library's target (for example,
+`-DDiagnostics=true`); their defaults may differ (for example, `MultipleHeaders` defaults to `false` in Meson, while
+`JSON_MultipleHeaders` is `ON` in CMake). Meson requires this file next to `meson.build`, so it is also part of `include.zip`. `make check_build_options`
 ([`tools/check_build_options`](tools/check_build_options/README.md)) checks in CI that both files and the pkg-config files
 stay in sync with the CMake options.

@@ -1,5 +1,6 @@
 module(
    name = "nlohmann_json",
+    version = "3.12.0",
    compatibility_level = 1,
 )

@@ -1,4 +1,4 @@
-.PHONY: pretty clean ChangeLog.md release update_hedley update_hedley_undef BUILD.bazel natvis macro_builder_check check_build_options
+.PHONY: all amalgamate check-amalgamation check_build_options pretty install_astyle clean ChangeLog.md release update_hedley update_hedley_undef BUILD.bazel natvis macro_builder_check run_benchmarks pvs_studio serve_header reuse spdx

 ##########################################################################
 # configuration
@@ -41,12 +41,18 @@ all:
 	@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_build_options - check that the Meson build and the pkg-config files offer the options of the CMake target"
 	@echo "clean - remove built files"
-	@echo "fuzzing - see tests/fuzzing.md for how to build and run the fuzzers"
+	@echo "(fuzzers) - see tests/fuzzing.md, or run 'make -C tests fuzzers' to build the AFL fuzzers"
 	@echo "macro_builder_check - check that macro_scope.hpp matches tools/macro_builder's output"
 	@echo "natvis - regenerate nlohmann_json.natvis from the current ABI tags and version"
 	@echo "pretty - beautify code with Artistic Style"
+	@echo "pvs_studio - run the PVS-Studio static analyzer and open the report"
+	@echo "release - create the release files (include.zip, json.tar.xz, single headers, signatures, hashes)"
+	@echo "reuse - annotate the source files with REUSE license headers and lint them"
 	@echo "run_benchmarks - build and run benchmarks"
+	@echo "serve_header - serve the single header, re-amalgamated on demand (see tools/serve_header)"
+	@echo "spdx - generate the SPDX software bill of materials nlohmann_json.spdx"
 	@echo "update_hedley - download Hedley and regenerate hedley.hpp / hedley_undef.hpp"
 	@echo "update_hedley_undef - rebuild hedley_undef.hpp from the JSON_HEDLEY_* #define names in hedley.hpp"

@@ -108,13 +114,18 @@ $(AMALGAMATED_FWD_FILE): $(SRCS)
 $(AMALGAMATED_LITERALS_FILE): include/nlohmann/json_literals.hpp
 	cp include/nlohmann/json_literals.hpp $(AMALGAMATED_LITERALS_FILE)

+NATVIS_VENV=tools/generate_natvis/venv
+
 # regenerate nlohmann_json.natvis from the ABI tags and version in include/nlohmann/detail/abi_macros.hpp
+# (the dependencies are installed into a virtual environment first)
 natvis:
-	python3 tools/generate_natvis/generate_natvis.py .
+	@test -d $(NATVIS_VENV) || python3 -mvenv $(NATVIS_VENV)
+	@$(NATVIS_VENV)/bin/python3 -c 'import jinja2' 2>/dev/null || $(NATVIS_VENV)/bin/pip3 install --quiet -r tools/generate_natvis/requirements.txt
+	$(NATVIS_VENV)/bin/python3 tools/generate_natvis/generate_natvis.py .

 # regenerate the two tools/macro_builder blocks of $(MACRO_SCOPE_HPP) (see its README.md) and diff against the
 # checked-in header; phony, because it never writes $(MACRO_SCOPE_HPP) itself
-macro_builder_check:
+macro_builder_check: install_astyle
 	@set -e; \
 	TMPDIR=$$(mktemp -d ./macro_builder_check.XXXXXX); \
 	trap 'rm -rf "$$TMPDIR"' EXIT; \
@@ -131,27 +142,27 @@ macro_builder_check:
 check_build_options:
 	python3 tools/check_build_options/check_build_options.py .

-# check if file single_include/nlohmann/json.hpp has been amalgamated from the nlohmann sources
+# check if the single headers have been amalgamated from the nlohmann sources and if BUILD.bazel and
+# nlohmann_json.natvis are up to date; all checks are run, and the checked-in files are always restored
 check-amalgamation:
-	@mv $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~
-	@mv $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_FWD_FILE)~
-	@mv $(AMALGAMATED_LITERALS_FILE) $(AMALGAMATED_LITERALS_FILE)~
-	@$(MAKE) amalgamate
-	@diff $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE) ; false)
-	@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)
-	@diff $(AMALGAMATED_LITERALS_FILE) $(AMALGAMATED_LITERALS_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_LITERALS_FILE)~ $(AMALGAMATED_LITERALS_FILE) ; false)
-	@mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE)
-	@mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE)
-	@mv $(AMALGAMATED_LITERALS_FILE)~ $(AMALGAMATED_LITERALS_FILE)
-	@mv BUILD.bazel BUILD.bazel~
-	@$(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
-	@mv nlohmann_json.natvis nlohmann_json.natvis~
-	@$(MAKE) natvis
-	@diff nlohmann_json.natvis nlohmann_json.natvis~ || (echo "===================================================================\n  nlohmann_json.natvis is out of date! Please run 'make natvis'.\n===================================================================" ; mv nlohmann_json.natvis~ nlohmann_json.natvis ; false)
-	@mv nlohmann_json.natvis~ nlohmann_json.natvis
-	@$(MAKE) macro_builder_check
+	@status=0; \
+	banner() { printf '===================================================================\n  %s\n===================================================================\n' "$$1"; }; \
+	for FILE in $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE) BUILD.bazel nlohmann_json.natvis; do \
+	    mv "$$FILE" "$$FILE~" || exit 1; \
+	done; \
+	$(MAKE) amalgamate || status=1; \
+	$(MAKE) BUILD.bazel || status=1; \
+	$(MAKE) natvis || status=1; \
+	for FILE in $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE); do \
+	    diff "$$FILE" "$$FILE~" || { banner "$$FILE is out of date! Amalgamation required! Please read the contribution guidelines in file .github/CONTRIBUTING.md."; status=1; }; \
+	done; \
+	diff BUILD.bazel BUILD.bazel~ || { banner "BUILD.bazel is out of date! Please run 'make BUILD.bazel'."; status=1; }; \
+	diff nlohmann_json.natvis nlohmann_json.natvis~ || { banner "nlohmann_json.natvis is out of date! Please run 'make natvis'."; status=1; }; \
+	for FILE in $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE) BUILD.bazel nlohmann_json.natvis; do \
+	    mv "$$FILE~" "$$FILE"; \
+	done; \
+	$(MAKE) macro_builder_check || status=1; \
+	exit $$status

 # generate the Bazel BUILD file; phony, because a removed header would not trigger a rebuild
 BUILD.bazel:
@@ -212,8 +223,8 @@ release: include.zip json.tar.xz

 # clean up
 clean:
-	rm -fr fuzz fuzz-testing *.dSYM tests/*.dSYM
-	rm -fr cmake-build-benchmarks fuzz-testing cmake-build-pvs-studio release_files
+	rm -fr *.dSYM tests/*.dSYM tests/parse_*_fuzzer
+	rm -fr cmake-build-benchmarks cmake-build-pvs-studio release_files
 	$(MAKE) clean -Cdocs


@@ -10,10 +10,10 @@ SPDX-FileCopyrightText = "2013-2026 Niels Lohmann <https://nlohmann.me>"
 SPDX-License-Identifier = "MIT"

 [[annotations]]
-path = "include/nlohmann/thirdparty/hedley.hpp"
+path = "include/nlohmann/thirdparty/hedley/hedley.hpp"
 precedence = "aggregate"
 SPDX-FileCopyrightText = "2016-2021 Evan Nemerson <evan@nemerson.com>"
-SPDX-License-Identifier = "CC0"
+SPDX-License-Identifier = "CC0-1.0"

 [[annotations]]
 path = "include/nlohmann/detail/meta/cpp_future.hpp"
@@ -50,3 +50,9 @@ path = "tools/gdb_pretty_printer/**"
 precedence = "aggregate"
 SPDX-FileCopyrightText = "2020 Hannes Domani <https://github.com/ssbssa>"
 SPDX-License-Identifier = "MIT"
+
+[[annotations]]
+path = "docs/docset/icon*.png"
+precedence = "override"
+SPDX-FileCopyrightText = "JSON logo (public domain), https://commons.wikimedia.org/wiki/File:JSON_vector_logo.svg"
+SPDX-License-Identifier = "CC0-1.0"
@@ -5,15 +5,14 @@ set(N 10)
 # Needed tools.
 ###############################################################################

-include(FindPython3)
 find_package(Python3 COMPONENTS Interpreter)

-find_program(CLANG_TOOL NAMES clang++-HEAD clang++ clang++-22 clang++-21 clang++-20 clang++-19 clang++-18 clang++-17 clang++-16 clang++-15 clang++-14 clang++-13 clang++-12 clang++-11 clang++)
+find_program(CLANG_TOOL NAMES clang++ clang++-HEAD clang++-22 clang++-21 clang++-20 clang++-19 clang++-18 clang++-17 clang++-16 clang++-15 clang++-14 clang++-13 clang++-12 clang++-11)
 execute_process(COMMAND ${CLANG_TOOL} --version OUTPUT_VARIABLE CLANG_TOOL_VERSION ERROR_VARIABLE CLANG_TOOL_VERSION)
 string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" CLANG_TOOL_VERSION "${CLANG_TOOL_VERSION}")
 message(STATUS "🔖 Clang ${CLANG_TOOL_VERSION} (${CLANG_TOOL})")

-find_program(CLANG_TIDY_TOOL NAMES clang-tidy-22 clang-tidy-21 clang-tidy-20 clang-tidy-19 clang-tidy-18 clang-tidy-17 clang-tidy-16 clang-tidy-15 clang-tidy-14 clang-tidy-13 clang-tidy-12 clang-tidy-11 clang-tidy)
+find_program(CLANG_TIDY_TOOL NAMES clang-tidy clang-tidy-22 clang-tidy-21 clang-tidy-20 clang-tidy-19 clang-tidy-18 clang-tidy-17 clang-tidy-16 clang-tidy-15 clang-tidy-14 clang-tidy-13 clang-tidy-12 clang-tidy-11)
 execute_process(COMMAND ${CLANG_TIDY_TOOL} --version OUTPUT_VARIABLE CLANG_TIDY_TOOL_VERSION ERROR_VARIABLE CLANG_TIDY_TOOL_VERSION)
 string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" CLANG_TIDY_TOOL_VERSION "${CLANG_TIDY_TOOL_VERSION}")
 message(STATUS "🔖 Clang-Tidy ${CLANG_TIDY_TOOL_VERSION} (${CLANG_TIDY_TOOL})")
@@ -69,9 +68,7 @@ string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" VALGRIND_TOOL_VERSION "${VALGRIND_TOOL_V
 message(STATUS "🔖 Valgrind ${VALGRIND_TOOL_VERSION} (${VALGRIND_TOOL})")

 find_program(GENHTML_TOOL NAMES genhtml)
-find_program(PLOG_CONVERTER_TOOL NAMES plog-converter)
-find_program(PVS_STUDIO_ANALYZER_TOOL NAMES pvs-studio-analyzer)
-find_program(SCAN_BUILD_TOOL NAMES scan-build-15 scan-build-14 scan-build-13 scan-build-12 scan-build-11 scan-build)
+find_program(SCAN_BUILD_TOOL NAMES scan-build scan-build-22 scan-build-21 scan-build-20 scan-build-19 scan-build-18 scan-build-17 scan-build-16 scan-build-15 scan-build-14 scan-build-13 scan-build-12 scan-build-11)

 # the individual source files
 file(GLOB_RECURSE SRC_FILES ${PROJECT_SOURCE_DIR}/include/nlohmann/*.hpp)
@@ -367,7 +364,7 @@ add_custom_target(ci_test_coverage
    COMMAND ${LCOV_TOOL} --directory . --capture --output-file json.info --rc branch_coverage=1 --rc geninfo_unexecuted_blocks=1 --ignore-errors mismatch --ignore-errors unused
    COMMAND ${LCOV_TOOL} -e json.info ${SRC_FILES} --output-file json.info.filtered --rc branch_coverage=1 --ignore-errors unused
    COMMAND ${CMAKE_SOURCE_DIR}/tests/thirdparty/imapdl/filterbr.py json.info.filtered > json.info.filtered.noexcept
-    COMMAND genhtml --title "JSON for Modern C++" --legend --demangle-cpp --output-directory html --show-details --branch-coverage json.info.filtered.noexcept
+    COMMAND ${GENHTML_TOOL} --title "JSON for Modern C++" --legend --demangle-cpp --output-directory html --show-details --branch-coverage json.info.filtered.noexcept

    COMMENT "Compile and test with coverage"
 )
@@ -392,8 +389,8 @@ add_custom_target(ci_test_clang_sanitizer
 # Check if header is amalgamated and sources are properly indented.
 ###############################################################################

-# Same file set as .github/workflows/check_amalgamation.yml, so a direct push to develop/master/release/*
-# (which only this CMake target checks, not the pull_request-only workflow) is held to the same standard.
+# Same file set as .github/workflows/check_amalgamation.yml, so this CMake target (which can be run locally) is held
+# to the same standard as the workflow (which runs for pull requests and for pushes to develop/master/release/*).
 file(GLOB_RECURSE INDENT_FILES
    ${PROJECT_SOURCE_DIR}/docs/mkdocs/docs/examples/*.hpp
    ${PROJECT_SOURCE_DIR}/docs/mkdocs/docs/examples/*.cpp
@@ -423,7 +420,7 @@ add_custom_target(ci_test_amalgamation
    COMMAND ${Python3_EXECUTABLE} ${tool_dir}/amalgamate.py -c ${tool_dir}/config_json.json -s .
    COMMAND ${Python3_EXECUTABLE} ${tool_dir}/amalgamate.py -c ${tool_dir}/config_json_fwd.json -s .
    COMMAND cp ${PROJECT_SOURCE_DIR}/include/nlohmann/json_literals.hpp ${include_dir}/json_literals.hpp
-    COMMAND venv_astyle/bin/astyle --project=tools/astyle/.astylerc --suffix=none ${include_dir}/json.hpp ${include_dir}/json_fwd.hpp
+    COMMAND venv_astyle/bin/astyle --project=tools/astyle/.astylerc --suffix=none ${include_dir}/json.hpp ${include_dir}/json_fwd.hpp ${include_dir}/json_literals.hpp
    COMMAND ${CMAKE_COMMAND} -P ${PROJECT_SOURCE_DIR}/cmake/scripts/gen_bazel_build_file.cmake

    COMMAND diff ${include_dir}/json.hpp~ ${include_dir}/json.hpp
@@ -434,6 +431,8 @@ add_custom_target(ci_test_amalgamation
    COMMAND venv_astyle/bin/astyle --project=tools/astyle/.astylerc --suffix=orig ${INDENT_FILES}
    COMMAND for FILE in `find . -name '*.orig'`\; do false \; done

+    COMMAND rm -f ${include_dir}/json.hpp~ ${include_dir}/json_fwd.hpp~ ${include_dir}/json_literals.hpp~ ${PROJECT_SOURCE_DIR}/BUILD.bazel~
+
    WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
    COMMENT "Check amalgamation, formatting, and BUILD.bazel"
 )
@@ -611,9 +610,8 @@ foreach(SRC_FILE ${SRC_FILES})
    add_executable(single_${RELATIVE_SRC_FILE} EXCLUDE_FROM_ALL ${PROJECT_BINARY_DIR}/src_single/${RELATIVE_SRC_FILE}.cpp)
    target_include_directories(single_${RELATIVE_SRC_FILE} PRIVATE ${PROJECT_SOURCE_DIR}/include)
    target_compile_features(single_${RELATIVE_SRC_FILE} PRIVATE cxx_std_11)
-    if(RELATIVE_SRC_FILE STREQUAL "json" OR RELATIVE_SRC_FILE STREQUAL "json_literals")
-        # see below: report the diagnostics of json.hpp and json_literals.hpp without --error, so they
-        # do not fail the build
+    if(RELATIVE_SRC_FILE STREQUAL "json")
+        # see below: report the diagnostics of json.hpp without --error, so they do not fail the build
        set_property(TARGET single_${RELATIVE_SRC_FILE} PROPERTY CXX_INCLUDE_WHAT_YOU_USE ${IWYU_TOOL} -Xiwyu --max_line_length=300)
    else()
        set_property(TARGET single_${RELATIVE_SRC_FILE} PROPERTY CXX_INCLUDE_WHAT_YOU_USE "${iwyu_path_and_options}")
@@ -627,18 +625,31 @@ foreach(SRC_FILE ${SRC_FILES})
    # reporting its diagnostics (informational, via CXX_INCLUDE_WHAT_YOU_USE above) but exclude it
    # from the hard gate below so a fresh IWYU/compiler combination does not fail this target on a
    # nondeterministic suggestion for a header that already re-exports everything on purpose.
-    # json_literals.hpp and json.hpp include each other on purpose (json.hpp includes it at its end
-    # unless JSON_NO_AUTOMATIC_UDLS is defined), and IWYU, not following the cycle, suggests replacing
-    # json.hpp with json_fwd.hpp although the literals need the complete basic_json; exclude it, too.
-    if(NOT RELATIVE_SRC_FILE STREQUAL "json" AND NOT RELATIVE_SRC_FILE STREQUAL "json_literals")
+    if(NOT RELATIVE_SRC_FILE STREQUAL "json")
        list(APPEND single_binaries_tus src_single/${RELATIVE_SRC_FILE}.cpp)
    endif()
 endforeach()

+# The checks above look at each header on its own. Client code that includes only <nlohmann/json.hpp>
+# must not be told by include analyzers to include another nlohmann header for what it uses
+# (issue #5812): json.hpp marks those includes "IWYU pragma: export", and both IWYU and clang-tidy's
+# misc-include-cleaner (disabled in .clang-tidy for the library itself) check these clients.
+file(GLOB CONSUMER_FILES ${PROJECT_SOURCE_DIR}/tests/iwyu_consumer/*.cpp)
+foreach(CONSUMER_FILE ${CONSUMER_FILES})
+    get_filename_component(CONSUMER_NAME "${CONSUMER_FILE}" NAME_WE)
+    add_executable(iwyu_consumer_${CONSUMER_NAME} EXCLUDE_FROM_ALL ${CONSUMER_FILE})
+    target_include_directories(iwyu_consumer_${CONSUMER_NAME} PRIVATE ${PROJECT_SOURCE_DIR}/include)
+    target_compile_features(iwyu_consumer_${CONSUMER_NAME} PRIVATE cxx_std_11)
+    list(APPEND single_binaries iwyu_consumer_${CONSUMER_NAME})
+    list(APPEND single_binaries_tus ${CONSUMER_FILE})
+endforeach()
+
 if(IWYU_TOOL_PY)
    add_custom_target(ci_single_binaries
        DEPENDS ${single_binaries}
        COMMAND ${IWYU_TOOL_PY} -p ${PROJECT_BINARY_DIR} ${single_binaries_tus} -- ${iwyu_options}
+        COMMAND ${CLANG_TIDY_TOOL} -p ${PROJECT_BINARY_DIR} --checks=-*,misc-include-cleaner --warnings-as-errors=* ${CONSUMER_FILES}
+        VERBATIM
        COMMENT "Check if headers are self-contained"
    )
 else()
@@ -719,7 +730,7 @@ ci_get_cmake(4.0.0  CMAKE_4_0_0_BINARY)

 # the tests require CMake 3.13 or later, so they are excluded for CMake 3.5.0
 set(JSON_CMAKE_FLAGS_3_5_0 JSON_Diagnostics JSON_Diagnostic_Positions JSON_GlobalUDLs JSON_ImplicitConversions JSON_DisableEnumSerialization
-    JSON_LegacyDiscardedValueComparison JSON_Install JSON_MultipleHeaders JSON_SystemInclude JSON_Valgrind
+    JSON_DisableTupleReferenceConversion JSON_LegacyDiscardedValueComparison JSON_Install JSON_MultipleHeaders JSON_SystemInclude JSON_Valgrind
    JSON_StrictNulHandling JSON_StrictBinaryUTF8 JSON_DeleteDeprecatedFunctions)
 set(JSON_CMAKE_FLAGS_3_31_6 JSON_BuildTests ${JSON_CMAKE_FLAGS_3_5_0})
 set(JSON_CMAKE_FLAGS_4_0_0 JSON_BuildTests ${JSON_CMAKE_FLAGS_3_5_0})
@@ -776,17 +787,14 @@ add_custom_target(ci_cmake_flags
 # Use more installed compilers.
 ###############################################################################

-foreach(COMPILER g++-4.8 g++-4.9 g++-5 g++-6 g++-7 g++-8 g++-9 g++-10 g++-11 clang++-3.5 clang++-3.6 clang++-3.7 clang++-3.8 clang++-3.9 clang++-4.0 clang++-5.0 clang++-6.0 clang++-7 clang++-8 clang++-9 clang++-10 clang++-11 clang++-12 clang++-13 clang++-14 clang++-15 clang++-16 clang++-17 clang++-18 clang++-19 clang++-20)
+foreach(COMPILER g++-4.8 g++-4.9 g++-5 g++-6)
    find_program(COMPILER_TOOL NAMES ${COMPILER})
    if (COMPILER_TOOL)
-        unset(ADDITIONAL_FLAGS)
-
        add_custom_target(ci_test_compiler_${COMPILER}
            COMMAND CXX=${COMPILER} ${CMAKE_COMMAND}
                -DCMAKE_BUILD_TYPE=Debug -GNinja
                -DJSON_BuildTests=ON -DJSON_FastTests=ON
                -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_compiler_${COMPILER}
-                ${ADDITIONAL_FLAGS}
            COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_compiler_${COMPILER}
            COMMAND cd ${PROJECT_BINARY_DIR}/build_compiler_${COMPILER} && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
            COMMENT "Compile and test with ${COMPILER}"
@@ -800,7 +808,6 @@ add_custom_target(ci_test_compiler_default
        -DCMAKE_BUILD_TYPE=Debug -GNinja
        -DJSON_BuildTests=ON -DJSON_FastTests=ON
        -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_compiler_default
-        ${ADDITIONAL_FLAGS}
    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_compiler_default --parallel ${N}
    COMMAND cd ${PROJECT_BINARY_DIR}/build_compiler_default && ${CMAKE_CTEST_COMMAND} --parallel ${N} -LE git_required --output-on-failure
    COMMENT "Compile and test with default C++ compiler"
@@ -823,10 +830,12 @@ add_custom_target(ci_cuda_example

 add_custom_target(ci_module_cpp20
    COMMAND ${CMAKE_COMMAND}
-        -DCMAKE_BUILD_TYPE=Debug -GNinja 
+        -DCMAKE_BUILD_TYPE=Debug -GNinja
        -DJSON_CI=ON -DNLOHMANN_JSON_BUILD_MODULES=ON -DJSON_Install=ON
+        "-DCMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS}"
        -S${PROJECT_SOURCE_DIR}/tests/module_cpp20 -B${PROJECT_BINARY_DIR}/ci_module_cpp20
    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/ci_module_cpp20
+    VERBATIM
 )

 ###############################################################################
@@ -49,6 +49,7 @@ cc_library(
    hdrs = [
        "single_include/nlohmann/json.hpp",
        "single_include/nlohmann/json_fwd.hpp",
+        "single_include/nlohmann/json_literals.hpp",
    ],
    includes = ["single_include"],
    visibility = ["//visibility:public"],
@@ -7,12 +7,12 @@ This URL provides the most recent documentation and also applies to previous ver
 functions is not removed; instead, it is marked as deprecated.

 If you want to view the documentation for a specific tag or commit hash, you can generate it locally as follows (example
-using tag `v3.10.2`):
+using tag `v3.12.0`):

 ```shell
 git clone https://github.com/nlohmann/json.git
 cd json
-git checkout v3.10.2
+git checkout v3.12.0
 make install_venv serve -C docs/mkdocs
 ```

@@ -1,48 +1,24 @@
 SHELL=/usr/bin/env bash
-SED ?= $(shell which gsed 2>/dev/null || which sed)
-
-MKDOCS_PAGES=$(shell cd ../mkdocs/docs/ && find * -type f -name '*.md' | sort)
+PYTHON=../mkdocs/venv/bin/python3

 .PHONY: all
 all: JSON_for_Modern_C++.tgz

-docSet.dsidx: docSet.sql
-	# generate index
-	sqlite3 docSet.dsidx <docSet.sql
+# generate the search index (the docset target does this itself, this is
+# only handy for inspecting the index)
+docSet.dsidx: generate_docset.py
+	$(PYTHON) generate_docset.py index docSet.dsidx

-JSON_for_Modern_C++.docset: Info.plist docSet.dsidx
-	rm -fr JSON_for_Modern_C++.docset JSON_for_Modern_C++.tgz
-	mkdir -p JSON_for_Modern_C++.docset/Contents/Resources/Documents/
-	cp icon*.png JSON_for_Modern_C++.docset
-	cp Info.plist JSON_for_Modern_C++.docset/Contents
-	# build and copy documentation
+# build the documentation and turn it into a self-contained docset
+.PHONY: JSON_for_Modern_C++.docset
+JSON_for_Modern_C++.docset:
 	$(MAKE) install_venv -C ../mkdocs
 	$(MAKE) build -C ../mkdocs
-	cp -r ../mkdocs/site/* JSON_for_Modern_C++.docset/Contents/Resources/Documents
-	# patch CSS to hide navigation items
-	echo -e "\n\nheader, footer, nav.md-tabs, nav.md-tabs--active, div.md-sidebar--primary, a.md-content__button { display: none; }" >> "$$(ls JSON_for_Modern_C++.docset/Contents/Resources/Documents/assets/stylesheets/main.*.min.css)"
-	# fix spacing
-	echo -e "\n\ndiv.md-sidebar div.md-sidebar--secondary, div.md-main__inner { top: 0; margin-top: 0 }" >> "$$(ls JSON_for_Modern_C++.docset/Contents/Resources/Documents/assets/stylesheets/main.*.min.css)"
-	# remove "JSON for Modern C++" from page titles (fallback)
-	find JSON_for_Modern_C++.docset/Contents/Resources/Documents -type f -exec $(SED) -i 's| - JSON for Modern C++</title>|</title>|' {} +
-	# replace page titles with name from index, if available
-	for page in $(MKDOCS_PAGES); do \
-		case "$$page" in \
-			*/index.md) path=$${page/\/index.md/} ;; \
-			*)          path=$${page/.md/}        ;; \
-		esac; \
-		title=$$(sqlite3 docSet.dsidx "SELECT name FROM searchIndex WHERE path='$$path/index.html'" | tr '\n' ',' | $(SED) -e 's/,/, /g' -e 's/, $$/\n/'); \
-		if [ "x$$title" != "x" ]; then \
-			$(SED) -i "s%<title>.*</title>%<title>$$title</title>%" "JSON_for_Modern_C++.docset/Contents/Resources/Documents/$$path/index.html"; \
-		fi \
-	done
-	# clean up
-	rm JSON_for_Modern_C++.docset/Contents/Resources/Documents/sitemap.*
-	# copy index
-	cp docSet.dsidx JSON_for_Modern_C++.docset/Contents/Resources/
+	$(PYTHON) generate_docset.py docset ../mkdocs/site .

+.PHONY: JSON_for_Modern_C++.tgz
 JSON_for_Modern_C++.tgz: JSON_for_Modern_C++.docset
-	tar --exclude='.DS_Store' -cvzf JSON_for_Modern_C++.tgz JSON_for_Modern_C++.docset
+	$(PYTHON) generate_docset.py tgz .

 # install docset for Zeal documentation browser (https://zealdocs.org/)
 .PHONY: install_docset_zeal
@@ -52,26 +28,6 @@ install_docset_zeal: JSON_for_Modern_C++.docset
 	mkdir -p $$docset_root; \
 	cp -r JSON_for_Modern_C++.docset $$docset_root/

-# both targets below compare the docset search index with the mkdocs page
-# set. They share the same normalization (docs/foo/index.md and
-# docs/foo.md both become foo/index.html, the URL mkdocs itself would
-# give the page; the top-level index.md is excluded, as it is not part
-# of the hand-curated docSet.sql) and use comm(1) on two sorted lists
-# instead of running a sqlite3 query, or an O(n*m) nested shell loop,
-# once per page.
-DOCSET_INDEX_PATHS=$(shell sqlite3 docSet.dsidx "SELECT DISTINCT path FROM searchIndex" | sort)
-DOCSET_PAGE_PATHS=$(shell echo '$(MKDOCS_PAGES)' | tr ' ' '\n' | grep -v '^index\.md$$' | $(SED) -E 's@/index\.md$$@/index.html@; s@\.md$$@/index.html@' | sort)
-
-# list mkdocs pages missing from the docset index
-.PHONY: list_missing_pages
-list_missing_pages: docSet.dsidx
-	@comm -23 <(echo '$(DOCSET_PAGE_PATHS)' | tr ' ' '\n') <(echo '$(DOCSET_INDEX_PATHS)' | tr ' ' '\n')
-
-# list paths in the docset index without a corresponding mkdocs page
-.PHONY: list_removed_paths
-list_removed_paths: docSet.dsidx
-	@comm -13 <(echo '$(DOCSET_PAGE_PATHS)' | tr ' ' '\n') <(echo '$(DOCSET_INDEX_PATHS)' | tr ' ' '\n')
-
 .PHONY: clean
 clean:
 	rm -f docSet.dsidx
@@ -4,7 +4,8 @@ The folder contains the required files to create a [docset](https://kapeli.com/d
 documentation browsers like [Dash](https://kapeli.com/dash), [Velocity](https://velocity.silverlakesoftware.com), or
 [Zeal](https://zealdocs.org).

-The docset can be created with
+The docset (pages and search index) is generated by `generate_docset.py` from the mkdocs site and `mkdocs.yml`. It
+can be created with

 ```sh
 make JSON_for_Modern_C++.docset
@@ -12,6 +13,7 @@ make JSON_for_Modern_C++.docset

 The generated folder `JSON_for_Modern_C++.docset` can then be opened in the documentation browser. `make all` builds a
 `JSON_for_Modern_C++.tgz` archive instead, and `make install_docset_zeal` installs the docset for Zeal directly.
+`make docSet.dsidx` builds only the search index.

 A recent version is also part of the [Dash user contributions](https://github.com/Kapeli/Dash-User-Contributions/tree/master/docsets/JSON_for_Modern_C%2B%2B).

@@ -1,289 +0,0 @@
-DROP TABLE IF EXISTS searchIndex;
-CREATE TABLE searchIndex(id INTEGER PRIMARY KEY, name TEXT, type TEXT, path TEXT);
-CREATE UNIQUE INDEX anchor ON searchIndex (name, type, path);
-
-- API
-INSERT INTO searchIndex(name, type, path) VALUES ('adl_serializer', 'Class', 'api/adl_serializer/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('adl_serializer::from_json', 'Function', 'api/adl_serializer/from_json/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('adl_serializer::to_json', 'Function', 'api/adl_serializer/to_json/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('byte_container_with_subtype', 'Class', 'api/byte_container_with_subtype/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('byte_container_with_subtype::byte_container_with_subtype', 'Constructor', 'api/byte_container_with_subtype/byte_container_with_subtype/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('byte_container_with_subtype::clear_subtype', 'Method', 'api/byte_container_with_subtype/clear_subtype/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('byte_container_with_subtype::has_subtype', 'Method', 'api/byte_container_with_subtype/has_subtype/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('byte_container_with_subtype::operator!=', 'Operator', 'api/byte_container_with_subtype/operator_ne/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('byte_container_with_subtype::operator==', 'Operator', 'api/byte_container_with_subtype/operator_eq/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('byte_container_with_subtype::set_subtype', 'Method', 'api/byte_container_with_subtype/set_subtype/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('byte_container_with_subtype::subtype', 'Method', 'api/byte_container_with_subtype/subtype/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json', 'Class', 'api/basic_json/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('format_as', 'Function', 'api/basic_json/format_as/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::accept', 'Function', 'api/basic_json/accept/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::array', 'Function', 'api/basic_json/array/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::array_t', 'Type', 'api/basic_json/array_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::as_base_class', 'Method', 'api/basic_json/as_base_class/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::at', 'Method', 'api/basic_json/at/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::back', 'Method', 'api/basic_json/back/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::basic_json', 'Constructor', 'api/basic_json/basic_json/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::begin', 'Method', 'api/basic_json/begin/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::binary', 'Function', 'api/basic_json/binary/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::binary_t', 'Type', 'api/basic_json/binary_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::boolean_t', 'Type', 'api/basic_json/boolean_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::cbegin', 'Method', 'api/basic_json/cbegin/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::cbor_tag_handler_t', 'Enum', 'api/basic_json/cbor_tag_handler_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::cend', 'Method', 'api/basic_json/cend/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::clear', 'Method', 'api/basic_json/clear/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::contains', 'Method', 'api/basic_json/contains/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::count', 'Method', 'api/basic_json/count/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::crbegin', 'Method', 'api/basic_json/crbegin/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::crend', 'Method', 'api/basic_json/crend/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::default_object_comparator_t', 'Type', 'api/basic_json/default_object_comparator_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::diff', 'Function', 'api/basic_json/diff/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::dump', 'Method', 'api/basic_json/dump/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::emplace', 'Method', 'api/basic_json/emplace/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::emplace_back', 'Method', 'api/basic_json/emplace_back/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::empty', 'Method', 'api/basic_json/empty/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::end', 'Method', 'api/basic_json/end/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::end_pos', 'Method', 'api/basic_json/end_pos/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::erase', 'Method', 'api/basic_json/erase/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::error_handler_t', 'Enum', 'api/basic_json/error_handler_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::exception', 'Class', 'api/basic_json/exception/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::find', 'Method', 'api/basic_json/find/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::flatten', 'Method', 'api/basic_json/flatten/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_bjdata', 'Function', 'api/basic_json/from_bjdata/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_bson', 'Function', 'api/basic_json/from_bson/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_cbor', 'Function', 'api/basic_json/from_cbor/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_msgpack', 'Function', 'api/basic_json/from_msgpack/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_bon8', 'Function', 'api/basic_json/from_bon8/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::from_ubjson', 'Function', 'api/basic_json/from_ubjson/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::front', 'Method', 'api/basic_json/front/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::get', 'Method', 'api/basic_json/get/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::get_allocator', 'Function', 'api/basic_json/get_allocator/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::get_binary', 'Method', 'api/basic_json/get_binary/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::get_ptr', 'Method', 'api/basic_json/get_ptr/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::get_ref', 'Method', 'api/basic_json/get_ref/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::get_to', 'Method', 'api/basic_json/get_to/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::input_format_t', 'Enum', 'api/basic_json/input_format_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::insert', 'Method', 'api/basic_json/insert/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::invalid_iterator', 'Class', 'api/basic_json/invalid_iterator/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_array', 'Method', 'api/basic_json/is_array/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_binary', 'Method', 'api/basic_json/is_binary/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_boolean', 'Method', 'api/basic_json/is_boolean/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_discarded', 'Method', 'api/basic_json/is_discarded/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_null', 'Method', 'api/basic_json/is_null/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_number', 'Method', 'api/basic_json/is_number/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_number_float', 'Method', 'api/basic_json/is_number_float/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_number_integer', 'Method', 'api/basic_json/is_number_integer/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_number_unsigned', 'Method', 'api/basic_json/is_number_unsigned/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_object', 'Method', 'api/basic_json/is_object/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_primitive', 'Method', 'api/basic_json/is_primitive/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_string', 'Method', 'api/basic_json/is_string/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::is_structured', 'Method', 'api/basic_json/is_structured/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::items', 'Method', 'api/basic_json/items/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::json_base_class_t', 'Type', 'api/basic_json/json_base_class_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::json_serializer', 'Class', 'api/basic_json/json_serializer/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::max_size', 'Method', 'api/basic_json/max_size/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::merge_patch', 'Method', 'api/basic_json/merge_patch/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::meta', 'Function', 'api/basic_json/meta/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::number_float_t', 'Type', 'api/basic_json/number_float_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::number_integer_t', 'Type', 'api/basic_json/number_integer_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::number_unsigned_t', 'Type', 'api/basic_json/number_unsigned_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::object', 'Function', 'api/basic_json/object/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::object_comparator_t', 'Type', 'api/basic_json/object_comparator_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::object_t', 'Type', 'api/basic_json/object_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator ValueType', 'Operator', 'api/basic_json/operator_ValueType/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator value_t', 'Operator', 'api/basic_json/operator_value_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator[]', 'Operator', 'api/basic_json/operator[]/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator=', 'Operator', 'api/basic_json/operator=/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator+=', 'Operator', 'api/basic_json/operator+=/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator==', 'Operator', 'api/basic_json/operator_eq/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator!=', 'Operator', 'api/basic_json/operator_ne/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator<', 'Operator', 'api/basic_json/operator_lt/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator<=', 'Operator', 'api/basic_json/operator_le/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator>', 'Operator', 'api/basic_json/operator_gt/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator>=', 'Operator', 'api/basic_json/operator_ge/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::operator<=>', 'Operator', 'api/basic_json/operator_spaceship/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::out_of_range', 'Class', 'api/basic_json/out_of_range/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::other_error', 'Class', 'api/basic_json/other_error/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::parse', 'Function', 'api/basic_json/parse/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::parse_error', 'Class', 'api/basic_json/parse_error/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::parse_event_t', 'Enum', 'api/basic_json/parse_event_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::parser_callback_t', 'Type', 'api/basic_json/parser_callback_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::patch', 'Method', 'api/basic_json/patch/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::patch_inplace', 'Method', 'api/basic_json/patch_inplace/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::push_back', 'Method', 'api/basic_json/push_back/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::rbegin', 'Method', 'api/basic_json/rbegin/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::rend', 'Method', 'api/basic_json/rend/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::sax_parse', 'Function', 'api/basic_json/sax_parse/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::size', 'Method', 'api/basic_json/size/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::start_pos', 'Method', 'api/basic_json/start_pos/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::string_t', 'Type', 'api/basic_json/string_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::swap', 'Method', 'api/basic_json/swap/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::type', 'Method', 'api/basic_json/type/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::type_error', 'Class', 'api/basic_json/type_error/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::type_name', 'Method', 'api/basic_json/type_name/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::unflatten', 'Method', 'api/basic_json/unflatten/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::update', 'Method', 'api/basic_json/update/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_bjdata', 'Function', 'api/basic_json/to_bjdata/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_bson', 'Function', 'api/basic_json/to_bson/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_cbor', 'Function', 'api/basic_json/to_cbor/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_msgpack', 'Function', 'api/basic_json/to_msgpack/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_bon8', 'Function', 'api/basic_json/to_bon8/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_string', 'Method', 'api/basic_json/to_string/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::to_ubjson', 'Function', 'api/basic_json/to_ubjson/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::value', 'Method', 'api/basic_json/value/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::value_t', 'Enum', 'api/basic_json/value_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::with_t', 'Type', 'api/basic_json/with_t/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('basic_json::~basic_json', 'Method', 'api/basic_json/~basic_json/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('json', 'Class', 'api/json/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('json_pointer', 'Class', 'api/json_pointer/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('json_pointer::back', 'Method', 'api/json_pointer/back/index.html');
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-
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-INSERT INTO searchIndex(name, type, path) VALUES ('Binary Formats', 'Guide', 'features/binary_formats/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('Integration: Pkg-config', 'Guide', 'integration/pkg-config/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Iterators', 'Guide', 'features/iterators/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('JSON Pointer', 'Guide', 'features/json_pointer/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('nlohmann Namespace', 'Guide', 'features/namespace/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Types', 'Guide', 'features/types/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Types: Number Handling', 'Guide', 'features/types/number_handling/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Object Order', 'Guide', 'features/object_order/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Performance', 'Guide', 'features/performance/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Parsing', 'Guide', 'features/parsing/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Parsing: JSON Lines', 'Guide', 'features/parsing/json_lines/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Parsing: Parser Callbacks', 'Guide', 'features/parsing/parser_callbacks/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Parsing: Parsing and Exceptions', 'Guide', 'features/parsing/parse_exceptions/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Parsing: SAX Interface', 'Guide', 'features/parsing/sax_interface/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Parsing: Untrusted Input', 'Guide', 'features/parsing/untrusted_input/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Runtime Assertions', 'Guide', 'features/assertions/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Specializing enum conversion', 'Guide', 'features/enum_conversion/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Supported Macros', 'Guide', 'features/macros/index.html');
-
-- Macros
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_ASSERT', 'Macro', 'api/macros/json_assert/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_BRACE_INIT_COPY_SEMANTICS', 'Macro', 'api/macros/json_brace_init_copy_semantics/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_CPP_11', 'Macro', 'api/macros/json_has_cpp_11/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_CPP_17', 'Macro', 'api/macros/json_has_cpp_11/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_CPP_20', 'Macro', 'api/macros/json_has_cpp_11/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_CPP_26', 'Macro', 'api/macros/json_has_cpp_11/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_EXPERIMENTAL_FILESYSTEM', 'Macro', 'api/macros/json_has_filesystem/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_FILESYSTEM', 'Macro', 'api/macros/json_has_filesystem/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_RANGES', 'Macro', 'api/macros/json_has_ranges/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_STATIC_RTTI', 'Macro', 'api/macros/json_has_static_rtti/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_HAS_THREE_WAY_COMPARISON', 'Macro', 'api/macros/json_has_three_way_comparison/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_NOEXCEPTION', 'Macro', 'api/macros/json_noexception/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_NO_IO', 'Macro', 'api/macros/json_no_io/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_NO_THREAD_LOCAL', 'Macro', 'api/macros/json_no_thread_local/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_PRECISE_STREAM_POSITION', 'Macro', 'api/macros/json_precise_stream_position/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_SKIP_LIBRARY_VERSION_CHECK', 'Macro', 'api/macros/json_skip_library_version_check/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_SKIP_UNSUPPORTED_COMPILER_CHECK', 'Macro', 'api/macros/json_skip_unsupported_compiler_check/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_STRICT_BINARY_UTF8', 'Macro', 'api/macros/json_strict_binary_utf8/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_STRICT_NUL_HANDLING', 'Macro', 'api/macros/json_strict_nul_handling/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_THROW_USER', 'Macro', 'api/macros/json_throw_user/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_TRY_USER', 'Macro', 'api/macros/json_throw_user/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('JSON_USE_SIMDUTF', 'Macro', 'api/macros/json_use_simdutf/index.html');
-INSERT INTO searchIndex(name, type, path) VALUES ('Macros', 'Macro', 'api/macros/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES', 'Macro', 'api/macros/nlohmann_define_type_with_names/index.html');
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-INSERT INTO searchIndex(name, type, path) VALUES ('NLOHMANN_JSON_VERSION_PATCH', 'Macro', 'api/macros/nlohmann_json_version_major/index.html');
@@ -0,0 +1,532 @@
+#!/usr/bin/env python3
+
+"""Generate the Dash docset search index from the mkdocs sources."""
+
+import argparse
+import glob
+import hashlib
+import html
+import os
+import re
+import shutil
+import sqlite3
+import sys
+import tarfile
+import urllib.parse
+import urllib.request
+
+import yaml
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+MKDOCS_YML = os.path.join(HERE, '..', 'mkdocs', 'mkdocs.yml')
+PAGES = os.path.join(HERE, '..', 'mkdocs', 'docs')
+
+# api pages whose (name, type) cannot be derived by the heuristics
+OVERRIDES = {
+}
+
+DOCSET = 'JSON_for_Modern_C++.docset'
+TITLE_SUFFIX = ' - JSON for Modern C++</title>'
+
+# CSS rules appended to the stylesheet: hide navigation items and fix spacing
+# hide the navigation (the documentation browser has its own); Material's class selectors would win over element
+# selectors, hence the classes and !important
+CSS_PATCH = (
+    '\n\n.md-header, .md-footer, .md-tabs, .md-sidebar--primary, .md-content__button { display: none !important; }'
+    '\n\n.md-sidebar--secondary, .md-main__inner { top: 0 !important; margin-top: 0 !important; }'
+)
+
+USER_AGENT = ('Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 '
+              '(KHTML, like Gecko) Chrome/124.0 Safari/537.36')
+CONTENT_TYPE_EXT = {'image/svg+xml': '.svg', 'image/png': '.png', 'image/jpeg': '.jpg',
+                    'image/gif': '.gif', 'image/webp': '.webp'}
+
+# remote loads that are allowed to remain (URL -> reason)
+ALLOWED_REMOTE = {
+    # Material only loads this polyfill if the browser has no ResizeObserver
+    'https://unpkg.com/resize-observer-polyfill': 'fallback for browsers without ResizeObserver',
+}
+
+problems = []
+
+
+def problem(page, reason) -> None:
+    """Record a problem; all problems are reported at the end."""
+    problems.append(f'generate_docset.py: {page}: {reason}')
+
+
+class Loader(yaml.SafeLoader):
+    """YAML loader that tolerates the custom tags used in mkdocs.yml."""
+
+
+Loader.add_multi_constructor('', lambda loader, suffix, node: None)
+
+
+def walk_nav(items, groups=()):
+    """Yield (group titles, nav title or None, md path) for all nav leaves."""
+    for item in items:
+        if isinstance(item, str):
+            yield list(groups), None, item
+        elif isinstance(item, dict):
+            for title, value in item.items():
+                if isinstance(value, list):
+                    yield from walk_nav(value, groups + (str(title),))
+                else:
+                    yield list(groups), str(title), value
+
+
+def page_path(md_path) -> str:
+    """Map a markdown path to the HTML path of the rendered page."""
+    if md_path.endswith('/index.md'):
+        return md_path[:-len('index.md')] + 'index.html'
+    return md_path[:-len('.md')] + '/index.html'
+
+
+def read_page(md_path) -> str:
+    """Read a page (resolving a snippet include), return '' if it does not exist."""
+    try:
+        with open(os.path.join(PAGES, md_path), encoding='utf-8') as f:
+            text = f.read()
+        m = re.match(r'--8<-- "(.+)"\s*$', text)
+        if m:
+            with open(os.path.join(PAGES, m.group(1)), encoding='utf-8') as f:
+                text = f.read()
+        return text
+    except OSError:
+        return ''
+
+
+def clean(text) -> str:
+    """Strip tags and entities from a heading and normalize whitespace."""
+    text = text.replace('\\>', '\x00')  # escaped '>' is not the end of a tag
+    text = html.unescape(re.sub(r'</?[a-zA-Z][^>]*>', '', text)).replace('\x00', '>')
+    return re.sub(r'\s+', ' ', text).strip()
+
+
+def strip_fences(text) -> str:
+    """Remove fenced code blocks (their lines may start with '# ')."""
+    return re.sub(r'^(```|~~~).*?^\1[^\n]*$', '', text, flags=re.M | re.S)
+
+
+def get_h1(text):
+    """Return the cleaned first H1 of a page or None."""
+    body = strip_fences(text)
+    m = re.search(r'^# (.+)$', body, flags=re.M)
+    if m:
+        return clean(m.group(1))
+    m = re.search(r'<h1>(.*?)</h1>', body, flags=re.S)
+    return clean(m.group(1)) if m else None
+
+
+def split_top_level(text, seps=','):
+    """Split at separators that are not nested in <>, () or []."""
+    parts, depth, current = [], 0, ''
+    for c in text:
+        if c in '<([':
+            depth += 1
+        elif c in '>)]':
+            depth -= 1
+        if c in seps and depth <= 0:
+            parts.append(current)
+            current = ''
+        else:
+            current += c
+    parts.append(current)
+    return [p.strip() for p in parts if p.strip()]
+
+
+OPERATOR_SYMBOLS = ('<=>', '<<', '>>', '<=', '>=', '<', '>')
+
+
+def api_names(h1) -> list:
+    """Derive the entry names from the H1 of an api page."""
+    # hide the angle brackets of operators from the nesting detection
+    for i, sym in enumerate(OPERATOR_SYMBOLS):
+        h1 = h1.replace('operator' + sym, f'operator\x01{i}\x01')
+    names = []
+    for part in split_top_level(h1):
+        name = part.replace('\\', '').replace('nlohmann::', '')
+        name = re.sub(r'\x01(\d)\x01', lambda m: OPERATOR_SYMBOLS[int(m.group(1))], name)
+        # drop qualifiers like "operator<<(basic_json)", but keep "operator()"
+        if not name.endswith('operator()'):
+            name = re.sub(r'(?<=\w|[<>=!+\-*/\[\]])\([^()]*\)$', '', name)
+        if name not in names:
+            names.append(name)
+    return names
+
+
+def first_cpp_block(text):
+    """Return the first ```cpp block following the H1."""
+    m = re.search(r'^# .*?^```cpp\n(.*?)^```', text, flags=re.M | re.S)
+    return m.group(1) if m else None
+
+
+def api_type(name, decl):
+    """Determine the Dash entry type from name and declaration."""
+    parts = name.split('::')
+    last = parts[-1]
+    if name.startswith('operator""'):
+        return 'Literal'
+    if last.startswith('operator'):
+        return 'Operator'
+    if decl is None:
+        return None
+    if re.search(r'\benum\b', decl):
+        return 'Enum'
+    if re.search(r'^\s*(template\s*<.*>\s*)?(class|struct)\s+\w+\s*(final\b|[:{;<]|$)', decl, flags=re.M):
+        return 'Class'
+    if re.search(r'\busing\s+\w+\s*=', decl) or 'typedef' in decl:
+        return 'Type'
+    if len(parts) > 1 and last == parts[-2]:
+        return 'Constructor'
+    if last.startswith('~'):
+        return 'Method'
+    if re.search(r'\bstatic\b', decl) or len(parts) == 1 or parts[0] == 'std':
+        return 'Function'
+    return 'Method'
+
+
+def macro_names(h1) -> list:
+    """Split the H1 of a macro page into macro names."""
+    return [n.strip() for n in re.split(r'[,/]', h1) if n.strip()]
+
+
+def api_entries(md_path):
+    """Return the (name, type) pairs of an api page."""
+    if md_path in OVERRIDES:
+        return OVERRIDES[md_path]
+    if md_path == 'api/macros/index.md':
+        return [('Macros', 'Macro')]
+    text = read_page(md_path)
+    h1 = get_h1(text)
+    if not h1:
+        problem(md_path, 'no H1 found')
+        return []
+    if md_path.startswith('api/macros/'):
+        return [(n, 'Macro') for n in macro_names(h1)]
+    names = api_names(h1)
+    if not names:
+        problem(md_path, 'no names found')
+        return []
+    decl = first_cpp_block(text)
+    result = []
+    for name in names:
+        kind = api_type(name, decl)
+        if kind is None:
+            problem(md_path, f'no type determinable for {name}')
+        else:
+            result.append((name, kind))
+    return result
+
+
+def guide_entries(nav):
+    """Yield (name, type, md path) for all non-api nav pages."""
+    for groups, title, md_path in walk_nav(nav):
+        if md_path.startswith('api/') or md_path == 'index.md':
+            continue
+        if not md_path.endswith('.md'):
+            continue
+        groups = groups[1:]  # drop the top-level tab
+        if title is None:
+            title = get_h1(read_page(md_path))
+            if not title:
+                problem(md_path, 'no title found')
+                continue
+        # "Parsing: Parsing Untrusted Input" -> "Parsing: Untrusted Input"
+        if groups and title.startswith(groups[-1] + ' ') and title[len(groups[-1]) + 1:][:1].isupper():
+            title = title[len(groups[-1]) + 1:]
+        if md_path.endswith('/index.md') and groups and title == groups[-1]:
+            name = ': '.join(groups)
+        else:
+            name = ': '.join(groups + [title])
+        yield name, 'Guide', md_path
+
+
+def build_entries() -> list:
+    """Return the sorted list of (name, type, path) index entries."""
+    nav = load_mkdocs_yml()['nav']
+
+    entries = set()
+    for name, kind, md_path in guide_entries(nav):
+        entries.add((name, kind, page_path(md_path)))
+
+    api_root = os.path.join(PAGES, 'api')
+    on_disk = set()
+    for root, _, files in os.walk(api_root):
+        for file in files:
+            if file.endswith('.md'):
+                rel = os.path.relpath(os.path.join(root, file), PAGES)
+                on_disk.add(rel.replace(os.sep, '/'))
+    for _, _, md_path in walk_nav(nav):
+        if md_path.startswith('api/') and md_path not in on_disk:
+            problem(md_path, 'listed in nav but missing on disk')
+    for md_path in sorted(on_disk):
+        for name, kind in api_entries(md_path):
+            entries.add((name, kind, page_path(md_path)))
+    return sorted(entries)
+
+
+def write_index(entries, out) -> None:
+    """Write the entries into a SQLite search index."""
+    if os.path.exists(out):
+        os.remove(out)
+    con = sqlite3.connect(out)
+    con.execute('CREATE TABLE searchIndex(id INTEGER PRIMARY KEY, name TEXT, type TEXT, path TEXT)')
+    con.execute('CREATE UNIQUE INDEX anchor ON searchIndex (name, type, path)')
+    con.executemany('INSERT INTO searchIndex(name, type, path) VALUES (?, ?, ?)', entries)
+    con.commit()
+    con.close()
+
+
+def html_files(root):
+    """Yield all HTML files below root."""
+    for base, _, files in os.walk(root):
+        for file in files:
+            if file.endswith('.html'):
+                yield os.path.join(base, file)
+
+
+def read(path) -> str:
+    with open(path, encoding='utf-8') as f:
+        return f.read()
+
+
+def write(path, text) -> None:
+    with open(path, 'w', encoding='utf-8') as f:
+        f.write(text)
+
+
+def remove_source_widget(docs) -> None:
+    """Drop data-md-component=source so Material does not query api.github.com for the stars and version."""
+    pattern = re.compile(r'\sdata-md-component=(?:"source"|source\b)')
+    for path in html_files(docs):
+        text = read(path)
+        new = pattern.sub('', text)
+        if new != text:
+            write(path, new)
+
+
+def patch_titles(docs, entries) -> None:
+    """Strip the site name from all titles; use the index names where available."""
+    names = {}
+    for name, _, path in entries:
+        names.setdefault(path, []).append(name)
+    for file in html_files(docs):
+        rel = os.path.relpath(file, docs).replace(os.sep, '/')
+        text = read(file).replace(TITLE_SUFFIX, '</title>')
+        if rel in names:
+            title = html.escape(', '.join(names[rel]), quote=False)
+            text = re.sub(r'<title>.*?</title>', lambda _: f'<title>{title}</title>', text, count=1, flags=re.S)
+        write(file, text)
+
+
+IMG_RE = re.compile(r'<img\b[^>]*>', re.I)
+ATTR_RE = r'''(?:{0})\s*=\s*(?:"([^"]*)"|'([^']*)'|([^\s"'>]+))'''
+
+
+def attr(tag, name):
+    """Return the value of an attribute in a tag or None."""
+    m = re.search(r'(?<![\w-])' + ATTR_RE.format(name), tag, flags=re.I)
+    return next(g for g in m.groups() if g is not None) if m else None
+
+
+def is_remote(url) -> bool:
+    return re.match(r'(https?:)?//', url.strip(), flags=re.I) is not None
+
+
+def download(url, docs) -> str:
+    """Download url into assets/external and return the path relative to docs."""
+    u = urllib.parse.urlparse(url if not url.startswith('//') else 'https:' + url)
+    if u.scheme.lower() not in ('http', 'https'):
+        raise ValueError(f'not an http(s) URL: {url}')
+    req = urllib.request.Request(u.geturl(), headers={'User-Agent': USER_AGENT})
+    # (the scheme is checked above)
+    with urllib.request.urlopen(req, timeout=20) as r:  # nosec B310
+        data = r.read()
+        ctype = r.headers.get_content_type()
+    path = urllib.parse.unquote(u.path).lstrip('/')
+    ext = os.path.splitext(path)[1]
+    if u.query or not ext or path.endswith('/'):
+        digest = hashlib.sha1(url.encode(), usedforsecurity=False).hexdigest()[:12]
+        path = os.path.join(os.path.dirname(path), digest + CONTENT_TYPE_EXT.get(ctype, ext or '.bin'))
+    rel = os.path.normpath(os.path.join('assets', 'external', u.hostname, path))
+    out = os.path.join(docs, rel)
+    os.makedirs(os.path.dirname(out), exist_ok=True)
+    with open(out, 'wb') as f:
+        f.write(data)
+    return rel.replace(os.sep, '/')
+
+
+def localize_images(docs) -> None:
+    """Download remote images and rewrite their src; drop them on failure."""
+    cache = {}
+    for file in html_files(docs):
+        text = read(file)
+
+        def repl(m):
+            tag = m.group(0)
+            src = attr(tag, 'src')
+            if src is None or not is_remote(src):
+                return tag
+            if src not in cache:
+                try:
+                    cache[src] = download(src, docs)
+                except Exception as e:  # noqa: BLE001
+                    print(f'generate_docset.py: warning: cannot download {src}: {e}', file=sys.stderr)
+                    cache[src] = None
+            if cache[src] is None:
+                return attr(tag, 'alt') or ''
+            local = os.path.relpath(os.path.join(docs, cache[src]), os.path.dirname(file))
+            local = local.replace(os.sep, '/')
+            return re.sub(ATTR_RE.format('src'), lambda _: f'src="{local}"', tag, count=1, flags=re.I)
+
+        new = IMG_RE.sub(repl, text)
+        if new != text:
+            write(file, new)
+
+
+def load_mkdocs_yml() -> dict:
+    """Load mkdocs.yml, ignoring tags like !ENV and !!python/name."""
+    with open(MKDOCS_YML, encoding='utf-8') as f:
+        # (Loader is a yaml.SafeLoader)
+        return yaml.load(f, Loader=Loader)  # nosec B506
+
+
+def localize_site_urls(docs, site_url) -> None:
+    """Load assets that the theme's JavaScript references by absolute site URL from the docset.
+
+    The privacy plugin rewrites the mermaid loader to "<site_url>assets/external/unpkg.com/mermaid@11/...", so the
+    docset would fetch mermaid from the live site. __md_scope is the site root that Material defines in every page.
+    """
+    pattern = re.compile(r'"' + re.escape(site_url) + r'(assets/[^"]*)"')
+    for base, _, files in os.walk(docs):
+        for file in (f for f in files if f.endswith('.js')):
+            path = os.path.join(base, file)
+            text = read(path)
+            new = pattern.sub(r'new URL("\1",__md_scope).href', text)
+            if new != text:
+                write(path, new)
+
+
+def remote_loads(docs, site_url) -> list:
+    """Return 'file: url' strings for resources that would be loaded remotely."""
+    found = []
+    cdn = re.compile(r'https://(?:unpkg\.com|cdn\.jsdelivr\.net|cdnjs\.cloudflare\.com|'
+                     r'fonts\.googleapis\.com|fonts\.gstatic\.com)/[^\s"\'`)\\]*')
+    css_url = re.compile(r'url\(\s*["\']?((?:https?:)?//[^)"\']+)', re.I)
+    css_import = re.compile(r'@import\s+(?:url\(\s*)?["\']?((?:https?:)?//[^)"\'; ]+)', re.I)
+    for base, _, files in os.walk(docs):
+        for file in files:
+            path = os.path.join(base, file)
+            rel = os.path.relpath(path, docs)
+            urls = []
+            if file.endswith('.html'):
+                text = read(path)
+                for m in re.finditer(r'<[a-zA-Z][^>]*>', text):
+                    tag = m.group(0)
+                    for name in ('src', 'poster'):
+                        v = attr(tag, name)
+                        if v and is_remote(v):
+                            urls.append(v)
+                    v = attr(tag, 'srcset')
+                    if v:
+                        urls += [c.split()[0] for c in v.split(',') if c.strip() and is_remote(c.strip())]
+                    if re.match(r'<link\b', tag, flags=re.I):
+                        rel_attr = (attr(tag, 'rel') or '').lower()
+                        v = attr(tag, 'href')
+                        if v and is_remote(v) and re.search(r'stylesheet|icon|preload|modulepreload|manifest', rel_attr):
+                            urls.append(v)
+                urls += css_url.findall(text) + css_import.findall(text)
+            elif file.endswith('.css'):
+                text = read(path)
+                urls += css_url.findall(text) + css_import.findall(text)
+            elif file.endswith('.js'):
+                text = read(path)
+                urls += cdn.findall(text)
+                urls += re.findall(re.escape(site_url) + r'assets/[^\s"\'`)\\]*', text)
+            found += [f'{rel}: {u}' for u in urls if u not in ALLOWED_REMOTE]
+    return found
+
+
+def make_docset(site, out_dir) -> int:
+    entries = build_entries()
+    if problems:
+        print('\n'.join(problems), file=sys.stderr)
+        return 1
+    docset = os.path.join(out_dir, DOCSET)
+    docs = os.path.join(docset, 'Contents', 'Resources', 'Documents')
+    if os.path.exists(docset):
+        shutil.rmtree(docset)
+    shutil.copytree(site, docs)
+    for icon in ('icon.png', 'icon@2x.png'):
+        shutil.copy(os.path.join(HERE, icon), docset)
+    shutil.copy(os.path.join(HERE, 'Info.plist'), os.path.join(docset, 'Contents'))
+    write_index(entries, os.path.join(docset, 'Contents', 'Resources', 'docSet.dsidx'))
+
+    # patch CSS to hide navigation items and fix spacing
+    css = glob.glob(os.path.join(docs, 'assets', 'stylesheets', 'main.*.min.css'))
+    if len(css) != 1:
+        print(f'generate_docset.py: expected exactly one main.*.min.css, found {len(css)}', file=sys.stderr)
+        return 1
+    with open(css[0], 'a', encoding='utf-8') as f:
+        f.write(CSS_PATCH)
+
+    patch_titles(docs, entries)
+    remove_source_widget(docs)
+    for sitemap in glob.glob(os.path.join(docs, 'sitemap.*')):
+        os.remove(sitemap)
+
+    # make the docset self-contained
+    site_url = load_mkdocs_yml()['site_url']
+    localize_images(docs)
+    localize_site_urls(docs, site_url)
+    remote = remote_loads(docs, site_url)
+    if remote:
+        print('generate_docset.py: remote resources remain in the docset:', file=sys.stderr)
+        print('\n'.join('  ' + r for r in remote), file=sys.stderr)
+        return 1
+    return 0
+
+
+def make_tgz(out_dir) -> int:
+    docset = os.path.join(out_dir, DOCSET)
+    if not os.path.isdir(docset):
+        print(f'generate_docset.py: {docset} does not exist', file=sys.stderr)
+        return 1
+    with tarfile.open(os.path.join(out_dir, 'JSON_for_Modern_C++.tgz'), 'w:gz') as tar:
+        tar.add(docset, arcname=DOCSET, filter=lambda i: None if os.path.basename(i.name) == '.DS_Store' else i)
+    return 0
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    sub = parser.add_subparsers(dest='command', required=True)
+    sub.add_parser('list', help='print the index entries as TSV')
+    p = sub.add_parser('index', help='write the SQLite search index')
+    p.add_argument('out')
+    p = sub.add_parser('docset', help='build the docset from a built mkdocs site')
+    p.add_argument('site_dir')
+    p.add_argument('out_dir')
+    p = sub.add_parser('tgz', help='pack the docset into a tarball')
+    p.add_argument('out_dir')
+    args = parser.parse_args()
+
+    if args.command == 'docset':
+        return make_docset(args.site_dir, args.out_dir)
+    if args.command == 'tgz':
+        return make_tgz(args.out_dir)
+
+    entries = build_entries()
+    if problems:
+        print('\n'.join(problems), file=sys.stderr)
+        return 1
+    if args.command == 'list':
+        for entry in entries:
+            print('\t'.join(entry))
+    elif args.command == 'index':
+        write_index(entries, args.out)
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())
@@ -17,6 +17,7 @@ build: style_check

 style_check:
 	@cd docs ; ../venv/bin/python3 ../scripts/check_structure.py
+	@venv/bin/python3 ../docset/generate_docset.py list > /dev/null

 # check that all Mermaid diagrams parse (needs Node.js)
 # This target is used in the CI (ci_test_documentation_mermaid).
@@ -27,7 +27,7 @@ To store objects in C++, a type is defined by the template parameters explained

 ### Default type

-With the default values for `ArrayType` (`std::vector`) and `AllocatorType` (`std::allocator`), the default value for
+With the default values for `ArrayType` (`std::vector`) and `AllocatorType` (`std::allocator`), the default type for
 `array_t` is:

 ```cpp
@@ -241,4 +241,6 @@ Strong exception safety: if an exception occurs, the original value stays intact
 3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
   already supported by [`operator[]`](operator[].md), [`value`](value.md), [`find`](find.md), and other lookup
   functions.
-4. Added in version 2.0.0.
+4. Added in version 2.0.0. Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
+[`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is not
+a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
@@ -23,7 +23,7 @@ To store boolean values in C++, a type is defined by the template parameter  `Bo

 ### Default type

-With the default values for `BooleanType` (`#!cpp bool`), the default value for `boolean_t` is `#!cpp bool`.
+With the default values for `BooleanType` (`#!cpp bool`), the default type for `boolean_t` is `#!cpp bool`.

 ### Storage

@@ -10,6 +10,10 @@ bool contains(KeyType&& key) const;

 // (3)
 bool contains(const json_pointer& ptr) const;
+
+// (4)
+template<typename T>
+bool contains(T) const = delete;
 ```

 1. Check whether an element exists in a JSON object with a key equivalent to `key`. If the element is not found or the 
@@ -17,6 +21,9 @@ bool contains(const json_pointer& ptr) const;
 2. See 1. This overload is only available if `KeyType` is comparable with `#!cpp typename object_t::key_type` and
   `#!cpp typename object_comparator_t::is_transparent` denotes a type.
 3. Check whether the given JSON pointer `ptr` can be resolved in the current JSON value.
+4. Deleted: this overload is only available if `T` is an integral type and is declared as deleted, so that a call with
+   an integer `key` (for example, `#!cpp j.contains(0)`) fails to compile. Otherwise, the integer literal `0` would convert to
+   a null `#!cpp const char*` and, from there, to the key type, causing undefined behavior at runtime.

 ## Template parameters

@@ -39,6 +46,7 @@ bool contains(const json_pointer& ptr) const;
   is not an object, `#!cpp false` is returned.
 2. See 1.
 3. `#!cpp true` if the JSON pointer can be resolved to a stored value, `#!cpp false` otherwise.
+4. Deleted; a call with an integral argument does not compile.

 ## Exception safety

@@ -49,6 +57,7 @@ Strong exception safety: if an exception occurs, the original value stays intact
 1. The function does not throw exceptions.
 2. The function does not throw exceptions.
 3. The function does not throw exceptions.
+4. Deleted; a call with an integral argument does not compile.

 ## Complexity

@@ -7,12 +7,19 @@ size_type count(const typename object_t::key_type& key) const;
 // (2)
 template<typename KeyType>
 size_type count(KeyType&& key) const;
+
+// (3)
+template<typename T>
+size_type count(T) const = delete;
 ```

 1. Returns the number of elements with key `key`. If `ObjectType` is the default `std::map` type, the return value will
   always be `0` (`key` was not found) or `1` (`key` was found).
 2. See 1. This overload is only available if `KeyType` is comparable with `#!cpp typename object_t::key_type` and
   `#!cpp typename object_comparator_t::is_transparent` denotes a type.
+3. Deleted: this overload is only available if `T` is an integral type and is declared as deleted, so that a call with
+   an integer `key` (for example, `#!cpp j.count(0)`) fails to compile. Otherwise, the integer literal `0` would convert to
+   a null `#!cpp const char*` and, from there, to the key type, causing undefined behavior at runtime.

 ## Template parameters

@@ -59,6 +59,7 @@ Currently, only `remove`, `add`, and `replace` operations are generated.
 - [patch](patch.md) applies a JSON Patch
 - [patch_inplace](patch_inplace.md) applies a JSON Patch in place
 - [merge_patch](merge_patch.md) applies a JSON Merge Patch
+- [merge_diff](merge_diff.md) creates a diff as a JSON Merge Patch

 ## Version history

@@ -62,6 +62,9 @@ Linear.

 ## Notes

+Floating-point numbers are written with the fewest digits that read back as the same value (for `#!cpp double`; see
+[number handling](../../features/types/number_handling.md#number-serialization)).
+
 Binary values are serialized as an object containing two keys:

 - "bytes": an array of bytes as integers
@@ -97,3 +100,5 @@ Binary values are serialized as an object containing two keys:
 - Error handlers added in version 3.4.0.
 - Serialization of binary values added in version 3.8.0.
 - Error handler `keep` added in version 3.13.0.
+- Doubles are written with the shortest digits (Żmij instead of Grisu2) since version 3.13.0; about 0.1% of doubles are
+  written differently, most of them with fewer digits.
@@ -37,8 +37,8 @@ ignore
 :   ignore invalid UTF-8 sequences; all valid bytes are copied to the output unchanged, and invalid bytes are dropped

 keep
-:   keep invalid UTF-8 sequences unchanged; only meaningful for the binary formats mentioned above, since [`dump`]
-    (dump.md) itself must produce text, and `keep` there writes the ill-formed bytes to the output as is, so the
+:   keep invalid UTF-8 sequences unchanged; only meaningful for the binary formats mentioned above, since
+    [`dump`](dump.md) itself must produce text, and `keep` there writes the ill-formed bytes to the output as is, so the
    result is then not valid UTF-8 (but still equals the input bytes exactly, including around any well-formed
    characters, which are still escaped as usual)

@@ -10,12 +10,21 @@ template<typename KeyType>
 iterator find(KeyType&& key);
 template<typename KeyType>
 const_iterator find(KeyType&& key) const;
+
+// (3)
+template<typename T>
+iterator find(T) = delete;
+template<typename T>
+const_iterator find(T) const = delete;
 ```

 1. Finds an element in a JSON object with a key equivalent to `key`. If the element is not found or the
   JSON value is not an object, `end()` is returned.
 2. See 1. This overload is only available if `KeyType` is comparable with `#!cpp typename object_t::key_type` and
   `#!cpp typename object_comparator_t::is_transparent` denotes a type.
+3. Deleted: this overload is only available if `T` is an integral type and is declared as deleted, so that a call with
+   an integer `key` (for example, `#!cpp j.find(0)`) fails to compile. Otherwise, the integer literal `0` would convert to
+   a null `#!cpp const char*` and, from there, to the key type, causing undefined behavior at runtime.

 ## Template parameters

@@ -124,7 +124,8 @@ Linear in the size of the input.
 !!! warning "Deprecation"

    - Overload (2) replaces calls to `from_bjdata` with a pointer and a length as first two parameters, which has been
-      deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      deprecated in version 3.13.0. In version 4.0.0, this overload
+      will be deleted (`= delete`) rather than removed. Please replace all calls like
      `#!cpp from_bjdata(ptr, len, ...);` with `#!cpp from_bjdata(ptr, ptr+len, ...);`.

    You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
@@ -110,7 +110,8 @@ Linear in the size of the input.
 !!! warning "Deprecation"

    - Overload (2) replaces calls to `from_bon8` with a pointer and a length as first two parameters, which has been
-      deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      deprecated in version 3.13.0. In version 4.0.0, this overload
+      will be deleted (`= delete`) rather than removed. Please replace all calls like
      `#!cpp from_bon8(ptr, len, ...);` with `#!cpp from_bon8(ptr, ptr+len, ...);`.

    You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
@@ -126,7 +126,8 @@ Linear in the size of the input.
 !!! warning "Deprecation"

    - Overload (2) replaces calls to `from_bson` with a pointer and a length as first two parameters, which has been
-      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      deprecated in version 3.8.0. In version 4.0.0, this overload
+      will be deleted (`= delete`) rather than removed. Please replace all calls like
      `#!cpp from_bson(ptr, len, ...);` with `#!cpp from_bson(ptr, ptr+len, ...);`.
    - Overload (2) replaces calls to `from_bson` with a pair of iterators as their first parameter, which has been
      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
@@ -135,7 +135,8 @@ Linear in the size of the input.
 !!! warning "Deprecation"

    - Overload (2) replaces calls to `from_cbor` with a pointer and a length as first two parameters, which has been
-      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      deprecated in version 3.8.0. In version 4.0.0, this overload
+      will be deleted (`= delete`) rather than removed. Please replace all calls like
      `#!cpp from_cbor(ptr, len, ...);` with `#!cpp from_cbor(ptr, ptr+len, ...);`.
    - Overload (2) replaces calls to `from_cbor` with a pair of iterators as their first parameter, which has been
      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
@@ -127,7 +127,8 @@ Linear in the size of the input.
 !!! warning "Deprecation"

    - Overload (2) replaces calls to `from_msgpack` with a pointer and a length as first two parameters, which has been
-      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      deprecated in version 3.8.0. In version 4.0.0, this overload
+      will be deleted (`= delete`) rather than removed. Please replace all calls like
      `#!cpp from_msgpack(ptr, len, ...);` with `#!cpp from_msgpack(ptr, ptr+len, ...);`.
    - Overload (2) replaces calls to `from_msgpack` with a pair of iterators as their first parameter, which has been
      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
@@ -125,7 +125,8 @@ Linear in the size of the input.
 !!! warning "Deprecation"

    - Overload (2) replaces calls to `from_ubjson` with a pointer and a length as first two parameters, which has been
-      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
+      deprecated in version 3.8.0. In version 4.0.0, this overload
+      will be deleted (`= delete`) rather than removed. Please replace all calls like
      `#!cpp from_ubjson(ptr, len, ...);` with `#!cpp from_ubjson(ptr, ptr+len, ...);`.
    - Overload (2) replaces calls to `from_ubjson` with a pair of iterators as their first parameter, which has been
      deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
@@ -85,7 +85,7 @@ The class satisfies the following concept requirements:
 - [EqualityComparable](https://en.cppreference.com/w/cpp/named_req/EqualityComparable): JSON values can be compared with
  `==`, see [`operator==`](operator_eq.md).
 - [LessThanComparable](https://en.cppreference.com/w/cpp/named_req/LessThanComparable): JSON values can be compared with
-  `<`, see [`operator<`](operator_le.md).
+  `<`, see [`operator<`](operator_lt.md).
 - [Swappable](https://en.cppreference.com/w/cpp/named_req/Swappable): Any JSON lvalue or rvalue of can be swapped with
  any lvalue or rvalue of other compatible types, using unqualified function `swap`.
 - [NullablePointer](https://en.cppreference.com/w/cpp/named_req/NullablePointer): JSON values can be compared against
@@ -285,6 +285,7 @@ Access to the JSON value
 ### JSON Merge Patch functions

 - [**merge_patch**](merge_patch.md) - applies a JSON Merge Patch
+- [**merge_diff**](merge_diff.md) (_static_) - creates a diff as a JSON Merge Patch

 ## Static functions

@@ -62,5 +62,5 @@ same name. Hidden members remain accessible via [`as_base_class`](as_base_class.

 ## Version history

- Added in version 3.12.0.
+- Added in version 3.11.3.
 - Made a public member type in version 3.13.0; it was private before, so it could not be named outside the class.
@@ -0,0 +1,79 @@
+# <small>nlohmann::basic_json::</small>merge_diff
+
+```cpp
+static basic_json merge_diff(const basic_json& source,
+                             const basic_json& target);
+```
+
+Creates a [JSON Merge Patch](https://tools.ietf.org/html/rfc7396) so that value `source` can be changed into the value
+`target` by calling the [`merge_patch`](merge_patch.md) function. The patch contains only what differs: changed and
+added members with their new values, and removed members with the value `#!json null`. Nested objects are compared
+member by member; any other value that differs, including an array, is replaced as a whole.
+
+For two JSON values `source` and `target`, where `target` contains no object member whose value is `#!json null`, the
+following code always yields `#!cpp true` (for [`ordered_json`](../ordered_json.md), see the notes below):
+```cpp
+basic_json patched = source;
+patched.merge_patch(merge_diff(source, target));
+patched == target;
+```
+
+## Parameters
+
+`source` (in)
+:   JSON value to compare from
+
+`target` (in)
+:   JSON value to compare against
+
+## Return value
+
+a JSON Merge Patch to convert the `source` to `target`
+
+## Exception safety
+
+Strong guarantee: `source` and `target` are never modified.
+
+## Complexity
+
+Linear in the total number of values (including nested ones) in `source` and `target`, times the cost of a key-based
+object operation (looking up a key, or adding one to the patch): logarithmic for [`json`](../json.md), and linear for
+[`ordered_json`](../ordered_json.md) (see [`ordered_map` complexity](../ordered_map.md#complexity)). For
+`ordered_json`, diffing two objects with `n` and `m` members therefore takes O((n+m)²).
+
+## Notes
+
+- A merge patch uses `#!json null` to remove a member, so it cannot set a member to `#!json null`. As in RFC 7396, a
+  `#!json null` member of `target` is treated as absent: the patch removes the member from `source` instead of setting
+  it to `#!json null`. A member that is `#!json null` in both `source` and `target` is unchanged and left out of the
+  patch, so `source` keeps it.
+- A merge patch cannot reorder object members, and [`merge_patch`](merge_patch.md) appends added members at the end.
+  For [`ordered_json`](../ordered_json.md), the patched value therefore has the same members as `target`, but not
+  necessarily in the same order, and may compare unequal to it. The patch lists changed and removed members in the
+  order of `source`, followed by added members in the order of `target`.
+
+## Examples
+
+??? example
+
+    The following code shows how a JSON Merge Patch is created as a diff for two JSON values.
+
+    ```cpp
+    --8<-- "examples/merge_diff.cpp"
+    ```
+
+    Output:
+
+    ```json
+    --8<-- "examples/merge_diff.output"
+    ```
+
+## See also
+
+- [RFC 7396 (JSON Merge Patch)](https://tools.ietf.org/html/rfc7396)
+- [merge_patch](merge_patch.md) applies a JSON Merge Patch
+- [diff](diff.md) creates a diff as a JSON Patch
+
+## Version history
+
+- Added in version 3.13.0.
@@ -67,6 +67,7 @@ returned by `#!cpp (*this)[key]`); it is read as it was when `merge_patch()` was

 - [RFC 7396 (JSON Merge Patch)](https://tools.ietf.org/html/rfc7396)
 - [patch](patch.md) apply a JSON patch
+- [merge_diff](merge_diff.md) creates a diff as a JSON Merge Patch

 ## Version history

@@ -23,9 +23,10 @@ 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
+:   the type to store floating-point numbers. The type must be `#!cpp float`, `#!cpp double`, or
+    `#!cpp long double`. The parser converts `#!cpp float`, `#!cpp double`, and a `#!cpp long double` that is IEEE 754
+    binary64 itself. It converts other `#!cpp long double` formats with `#!cpp std::from_chars` where available, or
+    with `#!cpp std::strtold` otherwise. Serialization falls back to `#!cpp std::snprintf`. 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).
@@ -34,7 +35,7 @@ type to use.

 ### Default type

-With the default values for `NumberFloatType` (`double`), the default value for `number_float_t` is `#!cpp double`.
+With the default values for `NumberFloatType` (`double`), the default type for `number_float_t` is `#!cpp double`.

 ### Default behavior

@@ -51,9 +52,11 @@ With the default values for `NumberFloatType` (`double`), the default value for
 > interoperability can be achieved by implementations that expect no more precision or range than these provide, in the
 > sense that implementations will approximate JSON numbers within the expected precision.

-This implementation does exactly follow this approach, as it uses double precision floating-point numbers. Note values
-smaller than `-1.79769313486232e+308` and values greater than `1.79769313486232e+308` will be stored as NaN internally
-and be serialized to `null`.
+This implementation does exactly follow this approach, as it uses double precision floating-point numbers by default.
+Note that with the default `double`, numbers smaller than `-1.79769313486232e+308` or greater than
+`1.79769313486232e+308` are rejected during parsing with
+[`out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406). Non-finite values (NaN and infinity) can
+only be stored by assigning them directly and are serialized to `null`.

 During deserialization (from JSON text or any of the binary formats), a finite number that does not fit into
 `number_float_t` is rejected with [`out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406), for
@@ -31,7 +31,7 @@ to use.

 ### Default type

-With the default values for `NumberIntegerType` (`std::int64_t`), the default value for `number_integer_t` is
+With the default values for `NumberIntegerType` (`std::int64_t`), the default type for `number_integer_t` is
 `#!cpp std::int64_t`.

 ### Default behavior
@@ -32,7 +32,7 @@ the type to use.

 ### Default type

-With the default values for `NumberUnsignedType` (`std::uint64_t`), the default value for `number_unsigned_t` is
+With the default values for `NumberUnsignedType` (`std::uint64_t`), the default type for `number_unsigned_t` is
 `#!cpp std::uint64_t`.

 ### Default behavior
@@ -26,8 +26,7 @@ To store objects in C++, a type is defined by the template parameters described

 `StringType`
 :   the type of the keys or names (e.g., `std::string`). The comparison function `std::less<StringType>` is used to
-    order elements inside the container. `object_t::key_type` must be implicitly convertible to `string_t` (required by the
-    binary formats).
+    order elements inside the container.

 `AllocatorType`
 :   the allocator to use for objects (e.g., `std::allocator`)
@@ -37,7 +36,7 @@ To store objects in C++, a type is defined by the template parameters described
 ### Default type

 With the default values for `ObjectType` (`std::map`), `StringType` (`std::string`), and `AllocatorType`
-(`std::allocator`), the default value for `object_t` is:
+(`std::allocator`), the default type for `object_t` is:

 ```cpp
 // until C++14
@@ -286,4 +286,6 @@ Strong exception safety: if an exception occurs, the original value stays intact
 3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
   already supported by [`at`](at.md), [`value`](value.md), [`find`](find.md), and other lookup functions.
 4. Added in version 2.0.0. A missing array index in the const version is guarded by a runtime assertion since
-   version 3.13.0.
+   version 3.13.0. Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
+[`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is not
+a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
@@ -11,18 +11,17 @@ template<typename ScalarType>
 bool operator==(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)

 // since C++20
-class basic_json {
-    bool operator==(const_reference rhs) const noexcept;              // (1)
+bool operator==(const_reference rhs) const noexcept;             // (1)

-    template<typename ScalarType>
-    bool operator==(ScalarType rhs) const noexcept(/* see below */); // (2)
-};
+template<typename ScalarType>
+bool operator==(ScalarType rhs) const noexcept(/* see below */); // (2)
 ```

 1. Compares two JSON values for equality according to the following rules:
    - Two JSON values are equal if (1) neither value is discarded, and (2) they are of the same type and their stored
      values are the same according to their respective `operator==`.
-    - Integer and floating-point numbers are automatically converted before comparison.
+    - Integer and floating-point numbers are compared by their exact values, without converting the integer to
+      floating-point. For instance, `9007199254740993` and `9007199254740992.0` are not equal.

 2. Compares a JSON value and a scalar or a scalar and a JSON value for equality by converting the
   scalar to a JSON value and comparing both JSON values according to 1.
@@ -15,7 +15,8 @@ bool operator<(ScalarType lhs, const const_reference rhs) noexcept(/* see below
  following rules:
    - If either operand is discarded, the comparison yields `#!cpp false`.
    - If both operands have the same type, the values are compared using their respective `operator<`.
-    - Integer and floating-point numbers are automatically converted before comparison.
+    - Integer and floating-point numbers are compared by their exact values, without converting the integer to
+      floating-point. For instance, `9007199254740992.0` is less than `9007199254740993`.
    - In case `lhs` and `rhs` have different types, the values are ignored and the order of the types
      is considered, which is:
        1. null
@@ -2,22 +2,18 @@

 ```cpp
 // since C++20
-class basic_json {
-    std::partial_ordering operator<=>(const_reference rhs) const noexcept;  // (1)
+std::partial_ordering operator<=>(const_reference rhs) const noexcept;                   // (1)

-    template<typename ScalarType>
-    std::partial_ordering operator<=>(const ScalarType rhs) const noexcept(/* see below */); // (2)
-};
+template<typename ScalarType>
+std::partial_ordering operator<=>(const ScalarType rhs) const noexcept(/* see below */); // (2)
 ```

 1. 3-way compares two JSON values producing a result of type `std::partial_ordering` according to the following rules:
    - Two JSON values compare with a result of `std::partial_ordering::unordered` if either value is discarded.
    - If both JSON values are of the same type, the result is produced by 3-way comparing their stored values using
      their respective `operator<=>`.
-    - Integer and floating-point numbers are converted to their common type and then 3-way compared using their
-      respective `operator<=>`.
-      For instance, comparing an integer and a floating-point value will 3-way compare the first value converted to
-      floating-point with the second value.
+    - Integer and floating-point numbers are 3-way compared by their exact values, without converting the integer to
+      floating-point. For instance, `9007199254740993` compares greater than `9007199254740992.0`.
    - Otherwise, yields a result by comparing the type (see [`value_t`](value_t.md)).
  
 2. 3-way compares a JSON value and a scalar or a scalar and a JSON value by converting the scalar to a JSON value and
@@ -45,7 +45,7 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
  pointer inside the patch cannot be resolved, e.g., `-` in a "remove" operation or `1a` for an array; example:
  `"unresolved reference token '-'"`.
 - Throws [`out_of_range.405`](../../home/exceptions.md#jsonexceptionout_of_range405) if JSON pointer has no parent
-  ("add", "remove", "move")
+  ("remove", "move")
 - Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
  location has a parent that is neither an object nor an array.
 - Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
@@ -112,3 +112,6 @@ is thrown. In any case, the original value is not changed: the patch is applied
  location has a non-object/non-array parent in version 3.13.0.
 - Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper
  prefix of its "path" location instead of silently producing a corrupted result in version 3.13.0.
+- Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
+  [`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is
+  not a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
@@ -41,7 +41,7 @@ No guarantees, value may be corrupted by an unsuccessful patch operation.
  pointer inside the patch cannot be resolved, e.g., `-` in a "remove" operation or `1a` for an array; example:
  `"unresolved reference token '-'"`.
 - Throws [`out_of_range.405`](../../home/exceptions.md#jsonexceptionout_of_range405) if JSON pointer has no parent
-  ("add", "remove", "move")
+  ("remove", "move")
 - Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
  location has a parent that is neither an object nor an array.
 - Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
@@ -110,3 +110,6 @@ function throws an exception.
  location has a non-object/non-array parent in version 3.13.0.
 - Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper
  prefix of its "path" location instead of silently producing a corrupted result in version 3.13.0.
+- Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
+  [`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is
+  not a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
@@ -32,7 +32,7 @@ JSON class into byte-sized characters during deserialization.

 ### Default type

-With the default values for `StringType` (`std::string`), the default value for `string_t` is `#!cpp std::string`.
+With the default values for `StringType` (`std::string`), the default type for `string_t` is `#!cpp std::string`.

 ### Encoding

@@ -41,6 +41,8 @@ With (2), the bytes written before the exception remain in the output adapter.
  above 9223372036854775807, which BON8 cannot represent
 - Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if `j` contains a string that is not
  valid UTF-8
+- Throws [type_error.321](../../home/exceptions.md#jsonexceptiontype_error321) if `j` or a value nested in it is
+  discarded; example: `"cannot serialize discarded value to BON8"`

 ## Complexity

@@ -36,8 +36,9 @@ The function can throw the following exceptions:
 - Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) if an array index in a key is not a
  number; example: `"array index 'one' is not a number"`
 - Throws [`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) if a level becomes an array
-  (because one of its keys is `0`) and another key at that level cannot be an array index; example:
-  `"unresolved reference token 'x'"`
+  (because one of its keys is `0`) and another key at that level begins with a digit but is not a valid array index
+  (such as `1a`), or is `-`; example:
+  `"unresolved reference token '-'"`

 ## Complexity

@@ -80,3 +81,6 @@ Apart from these two cases, for a JSON value `j`, the following is always true:

 - Added in version 2.0.0.
 - Made the array/object decision independent of the object's iteration order in version 3.13.0.
+- Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
+  [`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is
+  not a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
@@ -119,6 +119,14 @@ changes to any JSON value.

 ## Notes

+!!! warning "`null` members are not missing"
+
+    The default value is used only if the key (or JSON Pointer) does not exist. A member that exists but is
+    `#!json null` is converted like any other value, so `#!cpp j.value("k", 0)` throws a
+    [`type_error.302`](../../home/exceptions.md#jsonexceptiontype_error302) if `"k"` is `#!json null`. See
+    [Access with default value](../../features/element_access/default_value.md)
+    for alternatives.
+
 !!! warning "Return type"

    The value function is a template, and the return type of the function is determined by the type of the provided
@@ -227,4 +235,6 @@ changes to any JSON value.
   [`operator[]`](operator[].md), [`at`](at.md), [`find`](find.md), and other lookup functions.
 3. Added in version 2.0.2. Extended to work with arrays in version 3.13.0, including fixing an issue where resolving
   `ptr` through an array unexpectedly threw `out_of_range` instead of returning the resolved element (or
-   `default_value`, as documented).
+   `default_value`, as documented). Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109)
+   instead of returning `default_value` for a one-character array index that is not a digit (e.g., `/x`) in version
+   3.13.0, as it already did for longer ones.
@@ -18,13 +18,11 @@ bool operator==(
    const json_pointer<RefStringTypeRhs>& rhs);                     // (2)

 // since C++20
-class json_pointer {
-    template<typename RefStringTypeRhs>
-    bool operator==(
-        const json_pointer<RefStringTypeRhs>& rhs) const noexcept;  // (1)
+template<typename RefStringTypeRhs>
+bool operator==(
+    const json_pointer<RefStringTypeRhs>& rhs) const noexcept;      // (1)

-    bool operator==(const string_t& rhs) const;                     // (2)
-};
+bool operator==(const string_t& rhs) const;                         // (2)
 ```

 1. Compares two JSON pointers for equality by comparing their reference tokens.
@@ -2,10 +2,8 @@

 ```cpp
 // since C++20
-class json_pointer {
-    template<typename RefStringTypeRhs>
-    std::strong_ordering operator<=>(const json_pointer<RefStringTypeRhs>& rhs) const noexcept; // *NOPAD*
-};
+template<typename RefStringTypeRhs>
+std::strong_ordering operator<=>(const json_pointer<RefStringTypeRhs>& rhs) const noexcept; // *NOPAD*
 ```

 3-way compares two JSON pointers by lexicographically comparing their sequences of reference tokens: corresponding
@@ -27,6 +27,7 @@ header. See also the [macro overview page](../../features/macros.md).

 - [**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
 - [**JSON_HAS_FILESYSTEM**<br>**JSON_HAS_EXPERIMENTAL_FILESYSTEM**](json_has_filesystem.md) - control `std::filesystem` support
+- [**JSON_HAS_RANGE_VIEW_CONVERSION**](json_has_range_view_conversion.md) - control construction from `std::ranges` views
 - [**JSON_HAS_RANGES**](json_has_ranges.md) - control `std::ranges` support
 - [**JSON_HAS_STATIC_RTTI**](json_has_static_rtti.md) - control RTTI (run time type information) support
 - [**JSON_HAS_STD_FORMAT**](json_has_std_format.md) - control `std::format`/`std::formatter` support
@@ -49,6 +49,6 @@ The default value is detected based on preprocessor macros such as `#!cpp __cplu

 ## Version history

- Added in version 3.10.5.
+- Added in version 3.10.0.
 - Added `JSON_HAS_CPP_23` in version 3.12.0.
 - Added `JSON_HAS_CPP_26` in version 3.13.0.
@@ -0,0 +1,43 @@
+# JSON_HAS_RANGE_VIEW_CONVERSION
+
+```cpp
+#define JSON_HAS_RANGE_VIEW_CONVERSION /* value */
+```
+
+This macro indicates whether a JSON array can be constructed directly from a C++20 range view (`std::ranges::view`),
+such as the result of `std::views::filter` or `std::views::transform`. Possible values are `1` when supported or `0`
+when unsupported.
+
+## Default definition
+
+The default value is `1` if [`JSON_HAS_RANGES`](json_has_ranges.md) is `1` and the compiler is not MinGW (that is,
+`#!cpp __MINGW32__` is not defined), and `0` otherwise.
+
+When the macro is not defined, the library will define it to its default value.
+
+!!! info "Known compiler/stdlib exclusions"
+
+    - **MinGW** -- disabled, because its `std::ranges` support is incomplete ([issue #4916](https://github.com/nlohmann/json/issues/4916)).
+    - All toolchains for which [`JSON_HAS_RANGES`](json_has_ranges.md#default-definition) is disabled.
+
+## Examples
+
+??? example
+
+    The code below forces the library to disable the conversion from range views:
+
+    ```cpp
+    #define JSON_HAS_RANGE_VIEW_CONVERSION 0
+    #include <nlohmann/json.hpp>
+
+    ...
+    ```
+
+## See also
+
+- [JSON_HAS_RANGES](json_has_ranges.md) - control `std::ranges` support
+- [Constructing from a C++20 range view](../../features/conversions.md#putting-values-in) - usage of the feature
+
+## Version history
+
+- Added in version 3.13.0.
@@ -20,7 +20,7 @@ When the macro is not defined, the library will define it to its default value.
    
    - **GCC 11.1.0** — disabled (the shipped `<ranges>` header has a syntax error; [issue #4440](https://github.com/nlohmann/json/issues/4440))
    - **libstdc++ < 11** — disabled (incomplete C++20 ranges support; [issue #4440](https://github.com/nlohmann/json/issues/4440))
-    - **Clang < 16 with libstdc++** — disabled (incomplete ranges support; [issue #4440](https://github.com/nlohmann/json/issues/4440))
+    - **Clang < 16 with libstdc++** — disabled (incomplete ranges support; [issue #5161](https://github.com/nlohmann/json/issues/5161))
    - **libc++ < 160000** — disabled (incomplete C++20 ranges support; [issue #4440](https://github.com/nlohmann/json/issues/4440))
    - **nvcc (CUDA) 12.0.x and 12.1.x** — disabled (the `enable_borrowed_range` variable-template syntax triggers a parse error
      under these two toolkit versions; fixed in CUDA 12.2; [issue #3907](https://github.com/nlohmann/json/issues/3907))
@@ -44,9 +44,12 @@ When the macro is not defined, the library will define it to its default value.

 - [JSON_HAS_CPP_11 / JSON_HAS_CPP_14 / JSON_HAS_CPP_17 / JSON_HAS_CPP_20 / JSON_HAS_CPP_23 /
  JSON_HAS_CPP_26](json_has_cpp_11.md) - set supported C++ standard
+- [JSON_HAS_RANGE_VIEW_CONVERSION](json_has_range_view_conversion.md) - control construction from `std::ranges` views
 - [JSON_HAS_STD_FORMAT](json_has_std_format.md) - a similar feature-detection macro, for `std::format`/`std::formatter`
  support

 ## Version history

 - Added in version 3.11.0.
+- Added the exclusions for libstdc++ < 11, Clang < 16 with libstdc++, libc++ < 16, and nvcc (CUDA) 12.0.x and 12.1.x in
+  version 3.13.0. Before, only GCC 11.1.0 was excluded.
@@ -20,7 +20,10 @@ The macro does not affect:
 - The binary readers ([`from_cbor`](../basic_json/from_cbor.md), [`from_msgpack`](../basic_json/from_msgpack.md),
  [`from_ubjson`](../basic_json/from_ubjson.md), [`from_bjdata`](../basic_json/from_bjdata.md),
  [`from_bson`](../basic_json/from_bson.md)): none of these formats requires a decoder to reject ill-formed UTF-8, so
-  they always return the bytes unchanged.
+  by default they return the bytes unchanged (`error_handler_t::keep`), independent of this macro. Pass an
+  `error_handler` argument explicitly to validate or sanitize the strings they read.
+- [`from_bon8`](../basic_json/from_bon8.md): BON8 always validates, because the UTF-8 lead bytes mark where a string
+  ends.

 ## Default definition

@@ -18,7 +18,8 @@ When enabled, comparisons involving at least one discarded JSON value yield resu
 | `>=`         | `#!cpp true`  |
 | `>`          | `#!cpp false` |

-Otherwise, comparisons involving at least one discarded JSON value always yield `#!cpp false`.
+Otherwise, comparisons involving at least one discarded JSON value yield `#!cpp false`, except for `!=`, which is the
+negation of `==` and yields `#!cpp true`.

 ## Default definition

@@ -190,3 +190,5 @@ void to_json(BasicJsonType& j, const B& b) {
 4. Added in version 3.12.0.
 5. Added in version 3.12.0.
 6. Added in version 3.12.0.
+
+All six macros were changed to allow an empty member list in version 3.13.0.
@@ -186,3 +186,6 @@ See the examples below for the concrete generated code.
 1. Added in version 3.9.0.
 2. Added in version 3.11.0.
 3. Added in version 3.11.3.
+
+All three macros were changed to work with any `basic_json` specialization (not only `nlohmann::json`) in version 3.12.0,
+and to allow an empty member list in version 3.13.0.
@@ -185,3 +185,6 @@ See the examples below for the concrete generated code.
 1. Added in version 3.9.0.
 2. Added in version 3.11.0.
 3. Added in version 3.11.3.
+
+All three macros were changed to work with any `basic_json` specialization (not only `nlohmann::json`) in version 3.12.0,
+and to allow an empty member list in version 3.13.0.
@@ -38,4 +38,6 @@ the library.

 ## Version history

- Added in version 3.11.0. Changed inline namespace name in version 3.11.2.
+- Added in version 3.11.0. Changed inline namespace name in version 3.11.2. Added the ABI tag `_dp` in
+  version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, and `_ekmo` in version 3.13.0; see
+  [`nlohmann` Namespace](../../features/namespace.md#structure).
@@ -14,7 +14,7 @@ These macros can be used to open and close the `nlohmann` namespace. See
 ## Default definition

 The default definitions open and close the `nlohmann` namespace. The precise definition of
-[`NLOHMANN_JSON_NAMESPACE_BEGIN`] varies as described [here](../../features/namespace.md#structure).
+`NLOHMANN_JSON_NAMESPACE_BEGIN` varies as described [here](../../features/namespace.md#structure).

 1. Default definition of `NLOHMANN_JSON_NAMESPACE_BEGIN`:

@@ -10,7 +10,7 @@ The library parses, stores, and serializes JSON values in memory. It does not op
 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)
+The primary threat is therefore **untrusted input**: JSON text or binary data (BJData, BON8, 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
@@ -54,10 +54,9 @@ flowchart LR
  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,
-  comparison, 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 [`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
+  comparison, hashing, [`merge_patch`](../api/basic_json/merge_patch.md), [`diff`](../api/basic_json/diff.md),
+  [`flatten`](../api/basic_json/flatten.md), and the binary writers, recurse only up to a fixed depth and continue with
+  an explicit stack below it. 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.
@@ -12,7 +12,7 @@ violations will result in a failed build.

 Note: C++20 modules support may hit compiler-specific issues not covered by the general compiler matrix below. See [Modules](../features/modules.md#known-issues) for known issues and workarounds.

-Note: Some modern features (like C++20 ranges or filesystem support) may be disabled on specific broken or incomplete toolchains even when standard feature-test macros indicate support. See [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md) and [`JSON_HAS_FILESYSTEM`](../api/macros/json_has_filesystem.md) for details on known exclusions.
+Note: Some modern features (like C++20 ranges or filesystem support) may be disabled on specific broken or incomplete toolchains even when standard feature-test macros indicate support. See [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md), [`JSON_HAS_RANGE_VIEW_CONVERSION`](../api/macros/json_has_range_view_conversion.md), and [`JSON_HAS_FILESYSTEM`](../api/macros/json_has_filesystem.md) for details on known exclusions.

 - [x] The library is compiled with 50+ different C++ compilers with different operating systems and platforms,
  including the oldest versions known to compile the library.
@@ -107,7 +107,7 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
 - [x] The library is compiled with all C++ language revisions (C++11, C++14, C++17, C++20, C++23, and C++26) to detect
  and fix language deprecations early.
 - [x] The library is checked for compiler warnings:
-  - On Clang, `-Weverything` is used with 8 exceptions.
+  - On Clang, `-Weverything` is used with 7 exceptions.

    ??? abstract "Clang warnings"

@@ -0,0 +1,51 @@
+#include <iostream>
+#include <iomanip>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+using namespace nlohmann::literals;
+
+int main()
+{
+    // the source document
+    json source = R"(
+        {
+            "title": "Goodbye!",
+            "author": {
+                "givenName": "John",
+                "familyName": "Doe"
+            },
+            "tags": [
+                "example",
+                "sample"
+            ],
+            "content": "This will be unchanged"
+        }
+    )"_json;
+
+    // the target document
+    json target = R"(
+        {
+            "title": "Hello!",
+            "author": {
+                "givenName": "John"
+            },
+            "tags": [
+                "example"
+            ],
+            "content": "This will be unchanged",
+            "phoneNumber": "+01-123-456-7890"
+        }
+    )"_json;
+
+    // create the patch
+    json patch = json::merge_diff(source, target);
+
+    // roundtrip
+    json patched_source = source;
+    patched_source.merge_patch(patch);
+
+    // output patch and roundtrip result
+    std::cout << std::setw(4) << patch << "\n\n"
+              << std::setw(4) << patched_source << std::endl;
+}
@@ -0,0 +1,22 @@
+{
+    "author": {
+        "familyName": null
+    },
+    "phoneNumber": "+01-123-456-7890",
+    "tags": [
+        "example"
+    ],
+    "title": "Hello!"
+}
+
+{
+    "author": {
+        "givenName": "John"
+    },
+    "content": "This will be unchanged",
+    "phoneNumber": "+01-123-456-7890",
+    "tags": [
+        "example"
+    ],
+    "title": "Hello!"
+}
@@ -347,6 +347,13 @@ struct adl_serializer<boost::optional<T>> {
 NLOHMANN_JSON_NAMESPACE_END
 ```

+!!! tip "`std::optional` needs no serializer"
+
+    Since version 3.12.0, `std::optional<T>` is supported out of the box when compiling with C++17
+    (`std::nullopt` is converted to and from `null`). Do not write an `adl_serializer` for it; this pattern is only
+    needed for types such as `boost::optional` or for custom semantics. See [Conversions](conversions.md) and
+    [Omitting a field when serializing `std::optional`](conversions.md#omitting-a-field-when-serializing-stdoptional).
+
 !!! note "ABI compatibility"

    Use [`NLOHMANN_JSON_NAMESPACE_BEGIN`](../api/macros/nlohmann_json_namespace_begin.md) and `NLOHMANN_JSON_NAMESPACE_END`
@@ -267,9 +267,10 @@ unsigned 8-bit integer. If no subtype is given, the generic binary subtype 0x00

 ### CBOR

-[CBOR](binary_formats/cbor.md) supports binary values, but no subtypes. Subtypes will be serialized as tags. Any binary
-value will be serialized as byte strings. The library will choose the smallest representation using the length of the
-byte array.
+[CBOR](binary_formats/cbor.md) supports binary values and subtypes. Any binary value will be serialized as a byte
+string; a subtype is serialized as a tag preceding it. When parsing, tags are only read back as subtypes with
+`cbor_tag_handler_t::store` (see [`from_cbor`](../api/basic_json/from_cbor.md)). The library will choose the smallest
+representation using the length of the byte array.

 ??? example "Example: serialize a binary value to CBOR"

@@ -217,7 +217,8 @@ json j = numbers;   // [1,2,3]
    ```

    This requires [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md) to be enabled and is unavailable on MinGW due
-    to incomplete C++20 ranges support there.
+    to incomplete C++20 ranges support there; see
+    [`JSON_HAS_RANGE_VIEW_CONVERSION`](../api/macros/json_has_range_view_conversion.md).

 ## Your own types

@@ -30,6 +30,47 @@ you want to access and a default value in case there is no value stored with tha
    | `#!cpp j.value("append", false)`            | `#!json true`                                        |
    | `#!cpp j.value("logLevel", "verbose")`      | `#!json "verbose"`                                   |

+## Nested values
+
+To read a value deep inside a document, pass a [JSON Pointer](../json_pointer.md) instead of a key. The default value is
+returned if the value at the pointer does not exist, including the case that an intermediate key is missing. There is
+no need to check each level with [`contains`](../../api/basic_json/contains.md) first.
+
+```cpp
+json j = {{"server", {{"port", 8080}}}, {"list", {10, 20}}};
+
+int port = j.value("/server/port"_json_pointer, 80);        // 8080
+int timeout = j.value("/server/limits/timeout"_json_pointer, 30); // 30 (missing intermediate key)
+int second = j.value("/list/1"_json_pointer, 0);            // 20 (numeric tokens index arrays)
+int third = j.value("/list/5"_json_pointer, 0);             // 0 (index out of range)
+
+bool has_port = j.contains("/server/port"_json_pointer);    // true
+bool has_host = j.contains("/server/host/name"_json_pointer); // false
+```
+
+If the path is only available as a dotted string such as `#!cpp "server.port"`, do not build the pointer by
+concatenating `#!cpp "/"` and the parts: keys containing `/` or `~` would be misinterpreted. Append each part as a
+reference token with [`operator/=`](../../api/json_pointer/operator_slasheq.md) instead. It escapes the token for you.
+
+```cpp
+json::json_pointer to_pointer(const std::string& dotted)
+{
+    json::json_pointer ptr;
+    std::istringstream in(dotted);
+    for (std::string token; std::getline(in, token, '.');)
+    {
+        ptr /= token;
+    }
+    return ptr;
+}
+
+int port = j.value(to_pointer("server.port"), 80);          // 8080
+int first = j.value(to_pointer("list.0"), 0);               // 10
+```
+
+The key `#!cpp "a/b"` yields the pointer `#!cpp "/a~1b"`; the dot-splitting itself is up to the caller, so keys
+containing `.` need a different separator.
+
 ## Notes

 !!! failure "Exceptions"
@@ -37,6 +78,31 @@ you want to access and a default value in case there is no value stored with tha
    - With string keys, `value` can only be used with objects. For other types, a [`basic_json::type_error`](../../home/exceptions.md#jsonexceptiontype_error306) is thrown.
    - With JSON Pointers, `value` can be used with both objects and arrays. For other types (null, boolean, number, string), a [`basic_json::type_error`](../../home/exceptions.md#jsonexceptiontype_error306) is thrown.

+!!! warning "`null` and mistyped members are not missing"
+
+    `value` returns the default value only if the key is **absent**. If the member exists, it is converted to the type
+    of the default value, even if it is `#!json null`. For `#!json {"k": null}`, the call `#!cpp j.value("k", 0)` throws
+    a [`basic_json::type_error`](../../home/exceptions.md#jsonexceptiontype_error302), and so does a member of another
+    type such as a string where a number is expected. The same holds for JSON Pointers.
+
+    To treat `#!json null` like a missing value, check for it explicitly:
+
+    ```cpp
+    int n = (j.contains("k") && !j["k"].is_null()) ? j["k"].get<int>() : 0;
+    ```
+
+    With C++17, [`get<std::optional<T>>()`](../../api/basic_json/get.md) maps `#!json null` to an empty optional. As
+    [`at`](../../api/basic_json/at.md) throws [`out_of_range`](../../home/exceptions.md#jsonexceptionout_of_range403)
+    for an absent key, use [`find`](../../api/basic_json/find.md) to cover both cases:
+
+    ```cpp
+    std::optional<int> n;                        // empty if "k" is absent or null
+    if (const auto it = j.find("k"); it != j.end())
+    {
+        n = it->get<std::optional<int>>();       // still throws for a non-number such as "text"
+    }
+    ```
+
 !!! warning "Return type"

    The value function is a template, and the return type of the function is determined by the type of the provided
@@ -63,3 +129,6 @@ you want to access and a default value in case there is no value stored with tha

 - [`value`](../../api/basic_json/value.md) for access with default value
 - documentation on [checked access](checked_access.md)
+- documentation on [JSON Pointer](../json_pointer.md)
+- [`contains`](../../api/basic_json/contains.md) to check whether a key or JSON Pointer exists
+- [`json_pointer::operator/=`](../../api/json_pointer/operator_slasheq.md) to build a pointer token by token
@@ -77,6 +77,10 @@ auto val2 = j.at(json::json_pointer("/nested/three/1"));    // false
 auto val3 = j.value(json::json_pointer("/nested/four"), 0); // 0
 ```

+To read a value with a fallback, use [`value`](../api/basic_json/value.md) with a JSON Pointer; to test for existence,
+use [`contains`](../api/basic_json/contains.md). Neither needs intermediate checks, see
+[Nested values](element_access/default_value.md#nested-values).
+
 !!! note "Creating intermediate levels that don't exist"

    See the [`operator[]` notes](../api/basic_json/operator%5B%5D.md#return-value) for how array vs. object is
@@ -126,6 +130,8 @@ auto j_original = j_flat.unflatten();
 ## See also

 - Class [`json_pointer`](../api/json_pointer/index.md)
+- Functions [`value`](../api/basic_json/value.md), [`contains`](../api/basic_json/contains.md), and
+  [`at`](../api/basic_json/at.md) accept JSON Pointers; see [Nested values](element_access/default_value.md#nested-values)
 - Function [`flatten`](../api/basic_json/flatten.md)
 - Function [`unflatten`](../api/basic_json/unflatten.md)
 - [JSON Patch](json_patch.md) - paths inside a patch are JSON Pointers
@@ -82,6 +82,45 @@ To override the built-in check, define `JSON_HAS_FILESYSTEM` or `JSON_HAS_EXPERI

 See [full documentation of `JSON_HAS_FILESYSTEM` and `JSON_HAS_EXPERIMENTAL_FILESYSTEM`](../api/macros/json_has_filesystem.md).

+## `JSON_HAS_RANGES`
+
+The library uses `std::ranges` (and concepts) where available, for example, to parse from C++20 ranges and to
+construct JSON arrays from range views. The library detects whether the standard library supports ranges and
+disables the support on toolchains with an incomplete implementation. To override the built-in check, define
+`JSON_HAS_RANGES` to `1` or `0`.
+
+See [full documentation of `JSON_HAS_RANGES`](../api/macros/json_has_ranges.md).
+
+## `JSON_HAS_RANGE_VIEW_CONVERSION`
+
+When `JSON_HAS_RANGES` is enabled (and the compiler is not MinGW), a JSON array can be constructed directly from a C++20
+range view such as `std::views::filter(...)`. To override the built-in check, define `JSON_HAS_RANGE_VIEW_CONVERSION` to
+`1` or `0`.
+
+See [full documentation of `JSON_HAS_RANGE_VIEW_CONVERSION`](../api/macros/json_has_range_view_conversion.md).
+
+## `JSON_HAS_STATIC_RTTI`
+
+The library detects whether the compiler supports run time type information (RTTI), which it needs, for instance, to
+exclude `std::any` from the candidate types of the implicit conversion on C++17. To override the built-in check, define
+`JSON_HAS_STATIC_RTTI` to `1` or `0`.
+
+See [full documentation of `JSON_HAS_STATIC_RTTI`](../api/macros/json_has_static_rtti.md).
+
+## `JSON_HAS_STD_FORMAT`
+
+When compiling with C++20 and a standard library that provides `<format>`, the library provides a `std::formatter`
+specialization for JSON values. To override the built-in check, define `JSON_HAS_STD_FORMAT` to `1` or `0`.
+
+See [full documentation of `JSON_HAS_STD_FORMAT`](../api/macros/json_has_std_format.md).
+
+## `JSON_HAS_THREE_WAY_COMPARISON`
+
+When the compiler and standard library support 3-way comparison (the spaceship operator `<=>`), the library provides it
+for JSON values. To override the built-in check, define `JSON_HAS_THREE_WAY_COMPARISON` to `1` or `0`.
+
+See [full documentation of `JSON_HAS_THREE_WAY_COMPARISON`](../api/macros/json_has_three_way_comparison.md).
+
 ## `JSON_NOEXCEPTION`

 Exceptions can be switched off by defining the symbol `JSON_NOEXCEPTION`.
@@ -204,9 +243,9 @@ See [full documentation of `JSON_USE_GLOBAL_UDLS`](../api/macros/json_use_global

 ## `JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`

-When defined to `1`, the library restores the legacy behavior in which a discarded value compared equal to itself. This
-behavior is [deprecated](../integration/migration_guide.md#miscellaneous-functions) and switched off (`0`) by
-default.
+When defined to `1`, the library restores the legacy behavior in which comparing a discarded value with `<=` or `>=`
+yields `#!cpp true` instead of `#!cpp false`. This behavior is
+[deprecated](../integration/migration_guide.md#miscellaneous-functions) and switched off (`0`) by default.

 See [full documentation of `JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](../api/macros/json_use_legacy_discarded_value_comparison.md).

@@ -1,6 +1,6 @@
 # JSON Merge Patch

-The library supports JSON Merge Patch ([RFC 7386](https://tools.ietf.org/html/rfc7386)) as a patch format.
+The library supports JSON Merge Patch ([RFC 7396](https://tools.ietf.org/html/rfc7396)) as a patch format.
 The merge patch format is primarily intended for use with the HTTP PATCH method as a means of describing a set of
 modifications to a target resource's content. This function applies a merge patch to the current JSON value.

@@ -9,6 +9,16 @@ syntax that closely mimics the document being modified. Unlike [JSON Patch](json
 express every kind of change (e.g., it cannot reorder array elements or remove a specific array element), but it is
 easier to read and write for object-shaped documents.

+The function [`merge_diff`](../api/basic_json/merge_diff.md) creates a merge patch that changes one JSON value into
+another.
+
+!!! tip "Not a general deep merge"
+
+    A merge patch is not a general deep merge: a `#!json null` value in the patch deletes the key from the target.
+    To merge two objects recursively (e.g., defaults and user settings), use
+    [`update`](../api/basic_json/update.md) with `merge_objects` set to `#!cpp true`; see
+    [Merging objects](modifying_values.md#merging-objects).
+
 ??? example

    The following code shows how a JSON Merge Patch is applied to a JSON document.
@@ -28,3 +38,5 @@ easier to read and write for object-shaped documents.
 - [JSON Patch and Diff](json_patch.md) - a more expressive alternative that describes a sequence of operations
 - [JSON Pointer](json_pointer.md) - the addressing scheme used by JSON Patch
 - Function [`merge_patch`](../api/basic_json/merge_patch.md)
+- Function [`merge_diff`](../api/basic_json/merge_diff.md)
+- Function [`update`](../api/basic_json/update.md) - merge objects, optionally recursively
@@ -35,8 +35,12 @@ the insertion happened — useful for "add if absent" semantics.

 ## Merging objects

-To merge one object into another, [`update`](../api/basic_json/update.md) copies all members from another object,
-overwriting existing keys (similar to Python's `dict.update`). This is the idiomatic way to combine two objects.
+To merge one object into another, [`update`](../api/basic_json/update.md) copies all members from another object
+(similar to Python's `dict.update`). This is the idiomatic way to combine two objects. It has two modes:
+
+- By default, the merge is shallow: existing keys are overwritten, even if both values are objects.
+- With `merge_objects = #!cpp true`, keys whose values are objects in both JSON values are merged recursively.
+  Everything else is overwritten. In particular, arrays are replaced, not concatenated.

 ??? example

@@ -50,9 +54,22 @@ overwriting existing keys (similar to Python's `dict.update`). This is the idiom
    --8<-- "examples/update.output"
    ```

-For a recursive merge that follows [RFC 7386](https://tools.ietf.org/html/rfc7386), see
-[JSON Merge Patch](merge_patch.md). To apply a sequence of well-defined edit operations, see
-[JSON Patch](json_patch.md).
+A common use of the recursive mode is combining defaults with user settings. Nested defaults that the user did not set
+are kept:
+
+```cpp
+json defaults = {{"log", {{"level", "info"}, {"file", "app.log"}}}, {"retries", 3}};
+json user_settings = {{"log", {{"level", "debug"}}}};
+
+json config = defaults;
+config.update(user_settings, true);
+// {"log":{"file":"app.log","level":"debug"},"retries":3}
+```
+
+[JSON Merge Patch](merge_patch.md) ([RFC 7396](https://tools.ietf.org/html/rfc7396)) also merges objects recursively,
+but it is a different tool: a `#!json null` in the patch means "remove this key". It is meant for applying merge patch
+documents (e.g., received via HTTP PATCH). To merge configuration-like objects, use `#!cpp update(..., true)`. To apply
+a sequence of well-defined edit operations, see [JSON Patch](json_patch.md).

 ## Removing elements

@@ -72,6 +89,7 @@ a.erase(1);             // [1,3,4]  (erase by index)

 - [`push_back`](../api/basic_json/push_back.md) / [`emplace_back`](../api/basic_json/emplace_back.md) - append to an array
 - [`emplace`](../api/basic_json/emplace.md) - insert into an object if the key is absent
- [`update`](../api/basic_json/update.md) - merge objects
+- [`update`](../api/basic_json/update.md) - merge objects (shallow, or recursive with `merge_objects`)
+- [`merge_patch`](../api/basic_json/merge_patch.md) - apply an RFC 7396 merge patch
 - [`erase`](../api/basic_json/erase.md) / [`clear`](../api/basic_json/clear.md) - remove elements
 - [JSON Patch and Diff](json_patch.md) and [JSON Merge Patch](merge_patch.md) - structured modifications
@@ -101,3 +101,9 @@ follows:

 - Introduced inline namespace (`json_v3_11_0[_abi-tag]*`) in version 3.11.0.
 - Changed structure of inline namespace in version 3.11.2.
+- Added ABI tag `_dp` ([`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md)) in version 3.12.0.
+- Added ABI tags `_bics` ([`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md)), `_psp`
+  ([`JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md)), `_snul`
+  ([`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md)), `_sbu8`
+  ([`JSON_STRICT_BINARY_UTF8`](../api/macros/json_strict_binary_utf8.md)), and `_ekmo`
+  ([`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](../api/macros/json_use_objects_for_enum_keyed_maps.md)) in version 3.13.0.
@@ -50,19 +50,13 @@ stack, however deeply it is nested.

 Once a value has been parsed, operations that walk it recursively -- serializing it with
 [`dump`](../../api/basic_json/dump.md), hashing it, copying it, comparing two values with `#!cpp ==`, `#!cpp <`, or (in
-C++20) `#!cpp <=>`, merging with [`update`](../../api/basic_json/update.md), and applying a
-[`merge_patch`](../../api/basic_json/merge_patch.md) -- descend at most 128 levels on the call stack and continue
+C++20) `#!cpp <=>`, merging with [`update`](../../api/basic_json/update.md), applying a
+[`merge_patch`](../../api/basic_json/merge_patch.md), creating a patch with [`diff`](../../api/basic_json/diff.md) or
+[`merge_diff`](../../api/basic_json/merge_diff.md), [`flatten`](../../api/basic_json/flatten.md), and the binary
+writers (`to_cbor`, `to_msgpack`, ...) -- descend at most 128 levels on the call stack and continue
 below that with an explicit stack instead, so none of them can exhaust the stack either, however deeply the value is
 nested. Destroying a value (its destructor) never recurses at all, regardless of nesting depth, for the same reason.

-!!! note "Not every operation is bounded yet"
-
-    [`diff`](../../api/basic_json/diff.md), [`flatten`](../../api/basic_json/flatten.md), and the binary writers
-    (`to_cbor`, `to_msgpack`, ...) still recurse once per nesting level; this is called out as work in progress in the
-    [assurance case](../../community/assurance_case.md#secure-design). A value deep enough to matter for these
-    operations would typically first have to survive parsing without hitting a self-imposed depth limit, as described
-    above.
-
 ## Input size

 The library does not limit the overall size of a JSON text; a value nested or wide enough will use memory
@@ -52,7 +52,7 @@ with `\uXXXX` sequences, so that the output contains only ASCII characters:
 ```cpp
 json j = "苹果";
 j.dump();               // "苹果"
-j.dump(-1, ' ', true);  // "苹果"
+j.dump(-1, ' ', true);  // "\u82f9\u679c"
 ```

 ## Handling invalid UTF-8
@@ -120,7 +120,7 @@ requirements are collected in [Template Parameter Requirements](template_paramet

 ### Default type

-With the default values for *ObjectType* (`std::map`), *StringType* (`std::string`), and *AllocatorType* (`std::allocator`), the default value for `object_t` is:
+With the default values for *ObjectType* (`std::map`), *StringType* (`std::string`), and *AllocatorType* (`std::allocator`), the default type for `object_t` is:

 ```cpp
 std::map<
@@ -177,7 +177,7 @@ json j = m;

 ### Default type

-With the default values for *ArrayType* (`std::vector`) and *AllocatorType* (`std::allocator`), the default value for `array_t` is:
+With the default values for *ArrayType* (`std::vector`) and *AllocatorType* (`std::allocator`), the default type for `array_t` is:

 ```cpp
 std::vector<
@@ -209,7 +209,7 @@ Unicode values are split by the JSON class into byte-sized characters during des

 ### Default type

-With the default values for *StringType* (`std::string`), the default value for `string_t` is `#!cpp std::string`.
+With the default values for *StringType* (`std::string`), the default type for `string_t` is `#!cpp std::string`.

 ### Encoding

@@ -234,7 +234,7 @@ String values are stored as pointers in a `basic_json` type. That is, for any ac

 ### Default type

-With the default values for *BooleanType* (`#!cpp bool`), the default value for `boolean_t` is `#!cpp bool`.
+With the default values for *BooleanType* (`#!cpp bool`), the default type for `boolean_t` is `#!cpp bool`.

 ### Storage

@@ -252,9 +252,9 @@ This description includes both integer and floating-point numbers. However, C++

 ### Default types

-With the default values for *NumberIntegerType* (`std::int64_t`), the default value for `number_integer_t` is `std::int64_t`.
-With the default values for *NumberUnsignedType* (`std::uint64_t`), the default value for `number_unsigned_t` is `std::uint64_t`.
-With the default values for *NumberFloatType* (`#!cpp double`), the default value for `number_float_t` is `#!cpp double`.
+With the default values for *NumberIntegerType* (`std::int64_t`), the default type for `number_integer_t` is `std::int64_t`.
+With the default values for *NumberUnsignedType* (`std::uint64_t`), the default type for `number_unsigned_t` is `std::uint64_t`.
+With the default values for *NumberFloatType* (`#!cpp double`), the default type for `number_float_t` is `#!cpp double`.

 ### Default behavior

@@ -281,7 +281,7 @@ As this range is a subrange of the exactly supported range [`INT64_MIN`, `INT64_

 > This specification allows implementations to set limits on the range and precision of numbers accepted. Since software that implements IEEE 754-2008 binary64 (double precision) numbers is generally available and widely used, good interoperability can be achieved by implementations that expect no more precision or range than these provide, in the sense that implementations will approximate JSON numbers within the expected precision.

-This implementation does exactly follow this approach, as it uses double precision floating-point numbers. Note values smaller than `#!c -1.79769313486232e+308` and values greater than `#!c 1.79769313486232e+308` will be stored as NaN internally and be serialized to `#!json null`.
+This implementation does exactly follow this approach, as it uses double precision floating-point numbers by default (see *NumberFloatType* above). Note that with the default `#!cpp double`, numbers smaller than `#!c -1.79769313486232e+308` or greater than `#!c 1.79769313486232e+308` are rejected during parsing with [`out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406). Non-finite values (NaN and infinity) can only be stored by assigning them directly and are serialized to `#!json null`.

 ### Storage

@@ -82,12 +82,13 @@ flowchart TD

    - Numbers with a decimal digit or scientific notation are always stored as `#!c double`.
    - The number types can be changed, see [Template number types](#template-number-types). 
-    - Integers are converted by the library's own digit parser. Floating-point numbers are converted with
-      [`std::from_chars`](https://en.cppreference.com/w/cpp/utility/from_chars) if the library is compiled with C++17
-      and the standard library supports it, then with an exact fast path for `#!c double` values with few significant
-      digits, and otherwise with the locale-aware
-      [`std::strtod`](https://en.cppreference.com/w/cpp/string/byte/strtof) (`std::strtof`/`std::strtold` for the
-      other floating-point types). Before version 3.13.0, the conversion was realized by
+    - The library converts integers and floating-point numbers itself, independent of the locale. Floating-point
+      numbers are correctly rounded (to nearest, ties to even). Only a `#!c long double` that is not IEEE 754 binary64
+      (e.g., the 80-bit x87 format) is converted with `#!cpp std::from_chars` where available, or else with
+      [`std::strtold`](https://en.cppreference.com/w/cpp/string/byte/strtof). For that call, the library temporarily
+      replaces the `.` with the decimal point of the current locale (which may be longer than one byte, e.g., in
+      `fa_IR.UTF-8`), so the result does not depend on the locale either. Changing the locale in another thread during
+      parsing is undefined behavior of the C library, though. Before version 3.13.0, the conversion was realized by
      [`std::strtoull`](https://en.cppreference.com/w/cpp/string/byte/strtoul),
      [`std::strtoll`](https://en.cppreference.com/w/cpp/string/byte/strtol), and `std::strtod`, respectively.

@@ -100,10 +101,10 @@ flowchart TD
 ### Number limits

 - Any 64-bit signed or unsigned integer can be stored without loss of precision.
- Numbers exceeding the limits of `#!c double` (i.e., numbers that after conversion via
-[`std::strtod`](https://en.cppreference.com/w/cpp/string/byte/strtof) are not satisfying
+- Numbers exceeding the limits of `#!c double` (i.e., numbers whose rounded value is not satisfying
 [`std::isfinite`](https://en.cppreference.com/w/cpp/numeric/math/isfinite) such as `#!c 1E400`) will throw exception
-[`json.exception.out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406) during parsing.
+[`json.exception.out_of_range.406`](../../home/exceptions.md#jsonexceptionout_of_range406) during parsing. Numbers too
+small for `#!c double` (such as `#!c 1E-400`) become zero, with the sign of the number.
 - Floating-point numbers are rounded to the next number representable as `double`. For instance
 `#!c 3.141592653589793238462643383279` is stored as [`0x400921fb54442d18`](https://float.exposed/0x400921fb54442d18).
 This is the same behavior as the code `#!c double x = 3.141592653589793238462643383279;`.
@@ -133,9 +134,10 @@ That is, `-0` is stored as a signed integer, but the serialization does not repr
 ### Number serialization

 - Integer numbers are serialized as is; that is, no scientific notation is used.
- Floating-point numbers are serialized as specified by the `#!c %g` printf modifier with 
-  [`std::numeric_limits<double>::max_digits10`](https://en.cppreference.com/w/cpp/types/numeric_limits/max_digits10)
-  significant digits. The rationale is to use the shortest representation while still allowing round-tripping.
+- Floating-point numbers are serialized with the fewest digits that read back as the same value (the closest such
+  digits if there are several), in the layout of the `#!c %g` printf modifier: `#!c 1.5`, `#!c 100.0`, `#!c 1e+100`.
+  Doubles are converted with the algorithm of [Żmij](https://github.com/vitaut/zmij), floats with Grisu2, which
+  can write more digits than necessary.

 !!! hint "Notes regarding precision of floating-point numbers"