ArduinoJson

📟 JSON library for Arduino and embedded C++. Simple and efficient.

bblanchon

5530

998

C++

ArduinoJson is a C++ JSON library for Arduino and IoT (Internet Of Things).

Features

JSON deserialization
- Optionally decodes UTF-16 escape sequences to UTF-8
- Optionally supports comments in the input
- Optionally filters the input to keep only desired values
- Supports single quotes as a string delimiter
- Compatible with NDJSON and JSON Lines
JSON serialization
- Can write to a buffer or a stream
- Optionally indents the document (prettified JSON)
MessagePack serialization
MessagePack deserialization
Efficient
Versatile
- Supports custom allocators (to use external RAM chip, for example)
- Supports String, std::string, and std::string_view
- Supports Stream and std::istream/std::ostream
- Supports Flash strings
- Supports custom readers and custom writers
- Supports custom converters
Portable
- Usable on any C++ project (not limited to Arduino)
- Compatible with C11, C14 and C++17
- Support for C98/C03 available on ArduinoJson 6.20.x
- Zero warnings with -Wall -Wextra -pedantic and /W4
- Header-only library
- Works with virtually any board
  - Arduino boards: Uno, Due, Micro, Nano, Mega, Yun, Leonardo…
  - Espressif chips: ESP8266, ESP32
  - Lolin (WeMos) boards: D1 mini, D1 Mini Pro…
  - Teensy boards: 4.0, 3.2, 2.0
  - Particle boards: Argon, Boron, Electron, Photon…
  - Texas Instruments boards: MSP430…
  - Soft cores: Nios II…
- Tested on all major development environments
- Even works with online compilers like wandbox.org
- CMake friendly
Well designed
- Elegant API
- Thread-safe
- Self-contained (no external dependency)
- const friendly
- for friendly
- TMP friendly
- Handles integer overflows
Well tested
- Unit test coverage close to 100%
- Continuously tested on
- Continuously fuzzed with Google OSS Fuzz
- Passes all default checks of clang-tidy
Well documented
- Tutorials
- Examples
- How-tos
- FAQ
- Troubleshooter
- Book
- Changelog
Vibrant user community
- Most popular of all Arduino libraries on GitHub
- Used in hundreds of projects
- Responsive support

Quickstart

Deserialization

Here is a program that parses a JSON document with ArduinoJson.

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

JsonDocument doc;
deserializeJson(doc, json);

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

See the tutorial on arduinojson.org

Serialization

Here is a program that generates a JSON document with ArduinoJson:

JsonDocument doc;

doc["sensor"] = "gps";
doc["time"]   = 1351824120;
doc["data"][0] = 48.756080;
doc["data"][1] = 2.302038;

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