The Origins: 2001
Douglas Crockford is credited with discovering and popularizing JSON. In 2001, Crockford and colleagues were building a web application that needed to exchange data between server and browser without a full page reload. They realized they could use JavaScript object literal syntax.
The First JSON Library and RFC
Crockford registered json.org in 2001 and published the first JSON specification there. The format was so simple that implementations appeared in every major language within months. RFC 4627 was published in 2006, giving JSON official IETF recognition.
The Tipping Point Against XML
XML was dominant through the early 2000s. The rise of AJAX created demand for lightweight data exchange. Developers quickly discovered that JSON was easier to parse in JavaScript, produced smaller payloads, and required no special tooling. By 2010, most new APIs were using JSON.
JSON Today and Derivatives
JSON spawned a family of related formats. YAML is JSON-compatible with more human-friendly syntax. TOML is optimized for configuration files. JSON5 adds comments and trailing commas. BSON is MongoDB's wire format. JSON Schema defines structure. The ecosystem keeps growing.
JSON succeeded because it was simple enough to be defined in two pages, powerful enough to represent any data structure, and born at the exact moment the web needed lightweight data exchange.