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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 stores links to the input buffer (zero-copy)
  • 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
  • Twice smaller than the "official" Arduino_JSON library
  • Almost 10% faster than the "official" Arduino_JSON library
  • Consumes roughly 10% less RAM than the "official" Arduino_JSON library
  • Fixed memory allocation, no heap fragmentation
  • Optionally works without heap memory (zero malloc)
• Versatile
  • Supports custom allocators (to use external RAM chip, for example)
  • Supports Arduino's String and STL's std::string
  • Supports Arduino's Stream and STL's std::istream/std::ostream
  • Supports Flash strings
• Portable
  • Usable on any C++ project (not limited to Arduino)
  • Compatible with C++98
  • 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...
  • Tested on all major development environments
    • Arduino IDE
    • Atmel Studio
    • Atollic TrueSTUDIO
    • Energia
    • IAR Embedded Workbench
    • Keil uVision
    • MPLAB X IDE
    • PlatformIO
    • Sloeber plugin for Eclipse
    • Visual Micro
    • Visual Studio
  • Even works with online compilers like wandbox.org
• Well designed
  • Elegant API
  • Thread-safe
  • Self-contained (no external dependency)
  • const friendly
  • for friendly
  • TMP friendly
• Well tested
  • Unit test coverage close to 100%
  • Continuously tested on
    • Visual Studio 2010, 2012, 2013, 2015, 2017, 2019
    • GCC 4.4, 4.6, 4.7, 4.8, 4.9, 5, 6, 7, 8
    • Clang 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 6.0, 7, 8
  • Continuously fuzzed with Google OSS Fuzz
• Well documented
  • Tutorials
  • Examples
  • How-tos
  • FAQ
  • Book
• Vibrant user community
  • Most popular of all Arduino libraries on GitHub and PlatformIO
  • Used in hundreds of projects
  • Responsive support

Quickstart

Deserialization

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

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

DynamicJsonDocument doc(1024);
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:

DynamicJsonDocument doc(1024);

doc["sensor"] = "gps";
doc["time"]   = 1351824120;

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

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

See the tutorial on arduinojson.org

Support the project

Do you like this library? Please star this project on GitHub!

What? You don't like it but you love it? We don't take donations anymore, but we sell a book, so you can help and learn at the same time!