JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format that uses human-readable syntax to represent structured data as key-value pairs and ordered lists. Originally derived from JavaScript, JSON has become the dominant standard for data exchange across programming languages, APIs, and web services due to its simplicity, readability, and ease of parsing.
A JSON document consists of two primary structures: objects (enclosed in curly braces) containing comma-separated key-value pairs, and arrays (enclosed in square brackets) containing ordered sequences of values. Supported value types include strings, numbers, booleans, null, nested objects, and nested arrays. This minimal yet expressive grammar makes JSON both easy for humans to read and write, and efficient for machines to generate and parse.
JSON dominates modern web development as the default format for REST API request and response payloads, configuration files, NoSQL database documents (MongoDB, CouchDB), and message payloads in event-driven systems. While alternatives like Protocol Buffers and MessagePack offer better performance for high-throughput scenarios, and YAML provides more human-friendly syntax for configuration, JSON's ubiquitous tooling support and zero-dependency parsing in every major language keep it firmly in place as the default choice for data interchange.