A JSON module for Lua based on the very fast RapidJSON library.
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xpol Merge pull request #25 from matthewmjohnson/checkstack
Check lua stack when decoding objects and arrays
Latest commit 2b0742a Jul 27, 2018


RapidJSON bindings for Lua

License TrivisStatus AppVeyorStatus

A json module for LuaJIT 2.0/2.1 and Lua 5.1/5.2/5.3, based on the very fast RapidJSON C++ library.

See project homepage for more informations, bug report and feature request.


luarocks install rapidjson

or if you like to use your own version of RapidJSON, use:

luarocks install rapidjson RAPIDJSON_INCLUDE_DIRS=path/to/rapidjson/include/dir
local rapidjson = require('rapidjson')



Value Type Mappings

Lua Type JSON type Notes
rapidjson.null null
true true
false false
string string
table array when meta field __jsontype is 'array' or no __jsontype meta filed and table length > 0 or table length == 0 and empty_table_as_array option is specified
table object when not an array, all non string keys and its values are ignored.
number number


Clone or download source code, in the project root folder:

luarocks install dromozoa-utf8
luarocks install busted
luarocks make


To compare speed of rapidjson and other json libraries:

lua performance/run.lua


See API reference.

Release Steps

  1. Pass all unit tests.
  2. Update version in rapidjson-..*-1.rockspec and update the name of the rockspec file.
  3. Tag source code with that version (v*..), and push.
  4. luarocks upload rapidjson-*.*.*-1.rockspec



  • Added Document SchemaDocument SchemaValidator to support JSON pointer and schema.


  • Checks encoding error for float point numbers.
  • RapidJSON compiling turn: use release config and turn SIMD on if supported.


  • Fixes build and test errors introduced in 0.4.3.


  • CMakeLists.txt supports command line defined RAPIDJSON_INCLUDE_DIRS to specified RapidJSON include directory.
  • Keeps only necessary RapidJSON header files and docs make the rock much smaller.


  • Update RapidJSON to latest HEAD version.


  • Fixes Windows dll.


  • Checks circular reference when encoding tables.
  • A table is encoded as json array if:
    • have meta field __jsontype set to 'array'.
    • don't have meta filed __jsontype and length > 0.
  • When table is encoded as json object, only string keys and its values are encoded.
  • Integers are decoded to lua_Integer if it can be stored in lua_Integer.


  • Follow integers are encoded as integers.
    • Lua 5.3 integers.
    • Integers stored in double and in between:
      • [INT64_MIN..INT64_MAX] on 64 bit Lua or
      • [INT32_MIN..INT32_MAX] in 32 bit Lua.
  • CI scripts updated, thanks @ignacio


  • Rename module to rapidjson.
  • Added option.sort_keys option to rapidjson.encode() and rapidjson.dump(), and default value for sort_keys is false.
  • Added rapidjson._NAME ("rapidjson") and rapidjson._VERSION.
  • rapidjson.object() and rapidjson.array() just set metatable field __jsontype to 'object' and 'array' if passed table already have a metatable.
  • fixes dump return value of false rather than nil.


  • Initial release.