Lua CJSON is a fast JSON encoding/parsing module for Lua

JSON for Modern C++

A C++, header-only library for constructing JSON and JSON-like data formats, with JSON Pointer, JSON Patch, JSON Schema, JSONPath, JMESPath, CSV, MessagePack, CBOR, BSON, UBJSON

advanced, flexible JSON manipulation in C

Protocol Buffers - Google's data interchange format