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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)
  • Deduplicates strings
• 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 C++98, C++11, C++14 and C++17
  • 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
    • Particle
    • PlatformIO
    • Sloeber plugin for Eclipse
    • Visual Micro
    • Visual Studio
  • 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
    • Visual Studio 2010, 2012, 2013, 2015, 2017, 2019
    • GCC 4.4, 4.6, 4.7, 4.8, 4.9, 5, 6, 7, 8, 9, 10, 11
    • Clang 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 5.0, 6.0, 7, 8, 9, 10
  • 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.

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;
doc["data"][0] = 48.756080;
doc["data"][1] = 2.302038;

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

See the tutorial on arduinojson.org

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