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Niels Lohmann
52b72b5684
- Make the iterator range illustrations legible in dark mode (prefers-color-scheme rules inside the SVGs). - Add a "Byte layout" section with a color-coded byte table to each binary format page (BJData, BON8, BSON, CBOR, MessagePack, UBJSON), and highlight the smallest size per file in the comparison table. - Add "See also" sections to the overview pages that lacked one. - Split the release notes into one page per release, grouped by minor version on the overview page, with an "API changes" section per release generated from the API pages' version histories (hooks/api_changes.py). - Fact-check the release notes and version histories against the release tags and correct wrong or misleading entries (e.g., json_serializer 2.1.0, merge_patch 3.1.0, items, count, operator[], to_bjdata, std::string_view key support). Signed-off-by: Niels Lohmann <mail@nlohmann.me>
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Features
This section describes the features of the library in detail. If you are new to the library, the pages below are roughly ordered along a typical workflow: create or parse a value, access and modify it, convert it to and from your own C++ types, and finally serialize it again.
Creating and reading values
- Creating JSON values — build values from literals, initializer lists, and STL containers, and
understand the
#!cpp {}vs.#!cpp []ambiguity. - Parsing — read a JSON value from a string, file, or stream, including JSON Lines, callbacks, the SAX interface, error handling, and parsing untrusted input.
- Zero-copy JSON views — read a JSON text through a flat index instead of building a
jsontree; strings and numbers stay in the input and are only decoded when needed. - Editable documents — modify a parsed document without building a
jsontree. - Images — save a parsed document and load it again without parsing it.
- Comments and trailing commas — opt-in relaxations of the JSON grammar.
Accessing and modifying values
- Element access — unchecked (
operator[]), checked (at), and access with a default value. - JSON Pointer — address values deep inside a document with RFC 6901 pointers.
- Iterators — traverse arrays and objects.
- Modifying values — add, update, merge, and remove elements.
- JSON Patch and Diff and JSON Merge Patch — apply and compute structured changes.
Converting to and from C++ types
- Converting values — get values out with
get/get_to, and understand implicit conversions. - Arbitrary types conversions — teach the library about your own structs and classes.
- Specializing enum conversion — map enums to strings instead of integers.
Serializing values
- Serialization — turn a value back into JSON text with
dump, including pretty-printing and handling of non-ASCII and invalid UTF-8. - Binary formats — encode values more compactly as BJData, BON8, BSON, CBOR, MessagePack, or UBJSON.
- Binary values — store and exchange raw byte sequences.
How values are stored and configured
- Types and number handling — how JSON types map to C++ types and how numbers are treated.
- Template parameter requirements — what a type passed as one of
basic_json's template parameters has to provide. - Object order — keep insertion order with
ordered_json. - Performance — practical advice on parsing, memory use, serialization, and compile times.
- Runtime assertions, supported macros, the
nlohmannnamespace, and C++ modules — build-time and runtime configuration.
!!! tip "Looking for a specific function?"
This section gives conceptual overviews. For the precise signature, parameters, and return value of a function, see
the [API Documentation](../api/basic_json/index.md).
See also
- API documentation - reference of all classes and functions
- FAQ - answers to common questions
- Exceptions - all exceptions and their error codes
- Design goals
- Integration - how to add the library to a project