This library provides a C++ JSON parser and serializer optimized for performance and minimal code size, targeting developers who need a fast, lightweight, and hackable JSON solution for classic C++ environments. It aims to be significantly faster and smaller than modern C++ alternatives like nlohmann/json, while maintaining high conformance with the JSONTestSuite.

How It Works

The library employs a C-style parsing approach, prioritizing speed and simplicity over extensive C++ template metaprogramming. It leverages Google's double-conversion library for efficient floating-point serialization, preserving float precision without upcasting to double. This design choice results in a smaller codebase and faster compilation times compared to more feature-rich C++ JSON libraries.

Quick Start & Requirements

• Install: Compile json.cpp and json.h into your project.
• Dependencies: Google's double-conversion library.
• Links: JSONTestSuite

Highlighted Details

• Claims 2x-3x faster parsing and 10x faster compilation than nlohmann/json.
• Passes all JSONTestSuite conformance tests, with specific noted failures for certain UTF-8 edge cases.
• Preserves float precision during serialization, unlike libraries that upcast to double.
• Features a minimal codebase: 233 lines for json.h and 1,303 lines for json.cpp.

Maintenance & Community

Originally developed for Redbean in C, it was converted to C++ for Mozilla's llamafile project in 2024.

Licensing & Compatibility

The library is licensed under the MIT License, allowing for commercial use and integration into closed-source projects.

Limitations & Caveats

The library exhibits IMPLEMENTATION_FAIL for several JSONTestSuite cases related to malformed UTF-8, overlong sequences, and control codes within strings. It also fails on deeply nested arrays (depth_exceeded).