# ArduinoJson — Fast JSON Library for Embedded C++

> ArduinoJson is a memory-efficient JSON library for Arduino, ESP32, and embedded C++ projects. It handles parsing, serialization, and MessagePack with a zero-copy design optimized for constrained devices.

## Install

Save as a script file and run:

# ArduinoJson — Fast JSON Library for Embedded C++

## Quick Use
```cpp
#include <ArduinoJson.h>

JsonDocument doc;
doc["sensor"] = "temperature";
doc["value"] = 23.5;
serializeJson(doc, Serial);
```

## Introduction
ArduinoJson is a C++ JSON library designed for embedded systems. It provides a simple API for parsing and generating JSON with predictable memory usage, making it the standard choice for IoT firmware that communicates via JSON APIs.

## What ArduinoJson Does
- Parses JSON strings into a queryable document model
- Serializes C++ data structures to JSON or MessagePack
- Uses a fixed-size or dynamic memory pool to avoid heap fragmentation
- Supports JSON filtering to parse only the fields you need
- Handles nested objects, arrays, and streaming input

## Architecture Overview
ArduinoJson uses a JsonDocument that owns a contiguous memory pool. Parsing writes all values into this pool, avoiding scattered heap allocations. The library is header-only with no external dependencies, compiling on any C++11 toolchain from AVR to 64-bit desktop.

## Self-Hosting & Configuration
- Install via the Arduino Library Manager or PlatformIO
- Include the single header and create a JsonDocument with a size estimate
- Use the ArduinoJson Assistant at arduinojson.org to calculate memory requirements
- Configure stack vs heap allocation by choosing StaticJsonDocument or DynamicJsonDocument
- Works on Arduino, ESP8266, ESP32, STM32, Teensy, and standard Linux/macOS/Windows

## Key Features
- Header-only with zero external dependencies
- Predictable memory usage with no fragmentation
- Supports both JSON and MessagePack binary format
- JSON filtering reduces memory use by skipping unneeded fields
- Extensive test suite with over 3,000 unit tests

## Comparison with Similar Tools
- **cJSON** — plain C and smaller but lacks type safety and streaming; ArduinoJson is more ergonomic in C++
- **RapidJSON** — faster on desktop but uses more memory; ArduinoJson is optimized for MCUs
- **nlohmann/json** — beautiful API for desktop C++; too large for most embedded targets
- **Jansson** — C library with good API but no MessagePack support

## FAQ
**Q: How much RAM does ArduinoJson need?**
A: It depends on the document. A typical IoT payload with 5-10 fields uses 200-500 bytes. The online assistant calculates exact requirements.

**Q: Does it work on 8-bit AVR boards?**
A: Yes. ArduinoJson supports AVR, ARM, RISC-V, and Xtensa architectures with as little as 2KB RAM.

**Q: Can I parse streaming JSON?**
A: Yes. ArduinoJson can read from Stream objects (Serial, WiFiClient, File) without loading the entire string into memory.

**Q: Is ArduinoJson free for commercial use?**
A: Yes. It is released under the MIT license.

## Sources
- https://github.com/bblanchon/ArduinoJson
- https://arduinojson.org/

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Source: https://tokrepo.com/en/workflows/asset-7249eb89
Author: Script Depot