JSON is a lightweight data-interchange format. It can represent numbers, strings, ordered sequences of values, and collections of name/value pairs.

JsonCpp is a C++ library that allows manipulating JSON values, including serialization and deserialization to and from strings. It can also preserve existing comment in deserialization/serialization steps, making it a convenient format to store user input files.

Project Status

JsonCpp is a mature project in maintenance mode. Our priority is providing a stable, reliable JSON library for the long tail of C++ development.

Current Focus

Security: Addressing vulnerabilities and fuzzing results.
Compatibility: Ensuring the library builds without warnings on the latest versions of GCC, Clang, and MSVC.
Reliability: Fixing regressions and critical logical bugs.

Out of Scope

Performance: We are not competing with SIMD-accelerated or reflection-based parsers.
Features: We are generally not accepting requests for new data formats or major API changes.

JsonCpp remains a primary choice for developers who require comment preservation and support for legacy toolchains where modern C++ standards are unavailable. The library is intended to be a reliable dependency that does not require frequent updates or major migration efforts.

A note on backward-compatibility

1.y.z (master): Actively maintained. Requires C++11.
0.y.z: Legacy support for pre-C++11 compilers. Maintenance is limited to critical security fixes.
00.11.z: Discontinued.

Major versions maintain binary compatibility. Critical security fixes are accepted for both the master and 0.y.z branches.

Integration

Note: Package manager ports (vcpkg, Conan, etc.) are community-maintained. Please report outdated versions or missing generators to their respective repositories.

Meson

meson wrap install jsoncpp

Amalgamated source

For projects requiring a single-header approach, JsonCpp provides a script to generate an amalgamated source and header file.

You can generate the amalgamated files by running the following Python script from the top-level directory:

python3 amalgamate.py

This will generate a dist directory containing jsoncpp.cpp, json/json.h, and json/json-forwards.h. You can then drop these files directly into your project's source tree and compile jsoncpp.cpp alongside your other source files.

Documentation

The API reference is generated with Doxygen from the master branch on every push. To build it locally, run python3 doxybuild.py --open from the top-level directory (see doc/readme.txt). Additional information is available on the Project Wiki.

License

JsonCpp is licensed under the MIT license, or public domain where recognized. See LICENSE for details.