• Cross-platform
    • Compilers: Visual Studio, gcc, clang, etc.
    • Architectures: x86, x64, ARM, etc.
    • Operating systems: Windows, Mac OS X, Linux, iOS, Android, etc.
  • Easy installation
    • Header files only library. Just copy the headers to your project.
  • Self-contained, minimal dependences
    • No STL, BOOST, etc.
    • Only included <cstdio>, <cstdlib>, <cstring>, <inttypes.h>, <new>, <stdint.h>.
  • Without C++ exception, RTTI
  • High performance
    • Use template and inline functions to reduce function call overheads.
    • Internal optimized Grisu2 and floating point parsing implementations.
    • Optional SSE2/SSE4.2 support.

Standard compliance

  • RapidJSON should be fully RFC4627/ECMA-404 compliance.
  • Support JSON Pointer (RFC6901).
  • Support JSON Schema Draft v4.
  • Support Unicode surrogate.
  • Support null character ("\u0000")
    • For example, ["Hello\u0000World"] can be parsed and handled gracefully. There is API for getting/setting lengths of string.
  • Support optional relaxed syntax.
    • Single line (// ...) and multiple line (/* ... */) comments (kParseCommentsFlag).
    • Trailing commas at the end of objects and arrays (kParseTrailingCommasFlag).
    • NaN, Inf, Infinity, -Inf and -Infinity as double values (kParseNanAndInfFlag)
  • NPM compliant.


  • Support UTF-8, UTF-16, UTF-32 encodings, including little endian and big endian.
    • These encodings are used in input/output streams and in-memory representation.
  • Support automatic detection of encodings in input stream.
  • Support transcoding between encodings internally.
    • For example, you can read a UTF-8 file and let RapidJSON transcode the JSON strings into UTF-16 in the DOM.
  • Support encoding validation internally.
    • For example, you can read a UTF-8 file, and let RapidJSON check whether all JSON strings are valid UTF-8 byte sequence.
  • Support custom character types.
    • By default the character types are char for UTF8, wchar_t for UTF16, uint32_t for UTF32.
  • Support custom encodings.

API styles

  • SAX (Simple API for XML) style API
  • DOM (Document Object Model) style API


  • Recursive (default) and iterative parser
    • Recursive parser is faster but prone to stack overflow in extreme cases.
    • Iterative parser use custom stack to keep parsing state.
  • Support in situ parsing.
    • Parse JSON string values in-place at the source JSON, and then the DOM points to addresses of those strings.
    • Faster than convention parsing: no allocation for strings, no copy (if string does not contain escapes), cache-friendly.
  • Support 32-bit/64-bit signed/unsigned integer and double for JSON number type.
  • Support parsing multiple JSONs in input stream (kParseStopWhenDoneFlag).
  • Error Handling
    • Support comprehensive error code if parsing failed.
    • Support error message localization.

DOM (Document)

  • RapidJSON checks range of numerical values for conversions.
  • Optimization for string literal
    • Only store pointer instead of copying
  • Optimization for "short" strings
    • Store short string in Value internally without additional allocation.
    • For UTF-8 string: maximum 11 characters in 32-bit, 21 characters in 64-bit (13 characters in x86-64).
  • Optionally support std::string (define RAPIDJSON_HAS_STDSTRING=1)




  • Minimize memory overheads for DOM.
    • Each JSON value occupies exactly 16/20 bytes for most 32/64-bit machines (excluding text string).
  • Support fast default allocator.
    • A stack-based allocator (allocate sequentially, prohibit to free individual allocations, suitable for parsing).
    • User can provide a pre-allocated buffer. (Possible to parse a number of JSONs without any CRT allocation)
  • Support standard CRT(C-runtime) allocator.
  • Support custom allocators.


  • Some C++11 support (optional)
    • Rvalue reference
    • noexcept specifier
    • Range-based for loop