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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

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

See FAQ: Compatibility issues

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

Encoding / Generating

StaticJsonBuffer<200> jsonBuffer;

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

JsonArray& data = root.createNestedArray("data");
data.add(48.756080, 6);  // 6 is the number of decimals to print
data.add(2.302038, 6);   // if not specified, 2 digits are printed

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

See JsonGeneratorExample.ino

Documentation

The documentation is available online in the ArduinoJson wiki.

The ArduinoJson Assistant helps you get started with the library.

Testimonials

From Arduino's Forum user jflaplante:

I tried aJson json-arduino before trying your library. I always ran into memory problem after a while. I have no such problem so far with your library. It is working perfectly with my web services.

From StackOverflow user thegreendroid:

It has a really elegant, simple API and it works like a charm on embedded and Windows/Linux platforms. We recently started using this on an embedded project and I can vouch for its quality.

From GitHub user zacsketches:

Thanks for a great library!!! I've been watching you consistently develop this library over the past six months, and I used it today for a publish and subscribe architecture designed to help hobbyists move into more advanced robotics. Your library allowed me to implement remote subscription in order to facilitate multi-processor robots. ArduinoJson saved me a week's worth of time!!

From Reddit user erm_what_: