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
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
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

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

Sponsors

ArduinoJson is thankful to its sponsors. Please give them a visit; they deserve it!

If you run a commercial project that embeds ArduinoJson, think about sponsoring the library's development: it ensures the code that your products rely on stays actively maintained. It can also give your project some exposure to the makers' community.

If you are an individual user and want to support the development (or give a sign of appreciation), consider purchasing the book Mastering ArduinoJson ❤, or simply cast a star ⭐.