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 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 Deduplicates strings Versatile Supports custom allocators (to use external RAM chip, for example) Supports std::string_view Supports std::istream/std::ostream Supports Flash strings Supports custom writers Supports custom converters Portable Usable on any C++ project (not limited to Arduino) Compatible with C++11, C++14 and C++17 Support for C++98/C++03 available on ArduinoJson 6.20.x Zero warnings with -Wall -Wextra -pedantic and /W4 Header-only library Works with virtually any board Arduino boards: Nano, Leonardo... Espressif chips: ESP32 Lolin (WeMos) boards: D1 Mini Pro... Teensy boards: 2.0 Particle boards: Photon... Texas Instruments boards: MSP430... Soft cores: Nios II... 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 2017, 2019, 2022 GCC 4.8, 5, 6, 7, 8, 9, 10, 11, 12 Clang 7 to 19 Continuously fuzzed with Google OSS Fuzz Passes all default checks of clang-tidy Well documented Tutorials Examples How-tos FAQ Troubleshooter Book Changelog 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]} 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 cast a star ⭐.