• 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
  • Similar to SAX, RapidJSON provides a event sequential access parser API (rapidjson::GenericReader). It also provides a generator API (rapidjson::Writer) which consumes the same set of events.
  • DOM (Document Object Model) style API
  • Similar to DOM for HTML/XML, RapidJSON can parse JSON into a DOM representation (rapidjson::GenericDocument), for easy manipulation, and finally stringify back to JSON if needed.
  • The DOM style API (rapidjson::GenericDocument) is actually implemented with SAX style API (rapidjson::GenericReader). SAX is faster but sometimes DOM is easier. Users can pick their choices according to scenarios.


  • 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)


  • Support rapidjson::PrettyWriter for adding newlines and indentations.


  • Support rapidjson::GenericStringBuffer for storing the output JSON as string.
  • Support rapidjson::FileReadStream and rapidjson::FileWriteStream for input/output FILE object.
  • Support custom streams.


  • 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