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ArduinoJson - C++ JSON library for IoT

An elegant and efficient JSON library for embedded systems.

It's designed to have the most intuitive API, the smallest footprint and is able to work without any allocation on the heap (no malloc).

It has been written with Arduino in mind, but it isn't linked to Arduino libraries so you can use this library in any other C++ project. For instance, it supports Aduino's String and Stream, but also std::string, std::istream and std::ostream.

Features

JSON decoding (comments are supported)
JSON encoding (with optional indentation)
Elegant API, very easy to use
Fixed memory allocation (zero malloc)
No data duplication (zero copy)
Portable (written in C++98)
Self-contained (no external dependency)
Small footprint
Header-only library
MIT License

Works on

Arduino boards: Uno, Due, Mini, Micro, Yun...
ESP8266, ESP32
Teensy
RedBearLab boards (BLE Nano...)
Intel Edison and Galileo
WeMos boards: D1...
Computers: Windows, Linux, OSX...
PlatformIO
Particle
Energia

Quick start

Decoding / Parsing

char json[] = "{\"sensor\":\"gps\",\"time\":1351824120,\"data\":[48.756080,2.302038]}";

StaticJsonBuffer<200> jsonBuffer;

JsonObject& root = jsonBuffer.parseObject(json);

const char* sensor = root["sensor"];
long time          = root["time"];
double latitude    = root["data"][0];
double longitude   = root["data"][1];

See JsonParserExample.ino

Use ArduinoJson Assistant to compute the buffer size.

Encoding / Generating

StaticJsonBuffer<200> jsonBuffer;

JsonObject& root = jsonBuffer.createObject();
root["sensor"] = "gps";
root["time"] = 1351824120;

JsonArray& data = root.createNestedArray("data");
data.add(48.756080);
data.add(2.302038);

root.printTo(Serial);
// This prints:
// {"sensor":"gps","time":1351824120,"data":[48.756080,2.302038]}