JSON Reference
JSON syntax, structure, schema, and best practices — a practical reference for the format behind most modern APIs.
What is JSON?
JSON is a lightweight, language-independent format for structured data. Learn what it is, where it came from, and why it replaced XML for most APIs.
JSON Syntax
The complete grammar for valid JSON: the six value types, object and array structure, required string escapes, and what RFC 8259 actually specifies.
JSON Objects
JSON objects are unordered name/value pairs. Learn how duplicate keys actually behave, how nesting works, and practical patterns for structuring object data.
JSON Arrays
JSON arrays are ordered sequences of values — unlike objects, order is part of the guarantee. Learn how mixed-type arrays work and when to use an array instead of an object.
JSON Schema
JSON Schema is a separate specification for describing the structure and constraints JSON data should follow. Learn what it validates, its core keywords, and how it differs from JSON itself.
JSON Best Practices
JSON Best Practices separates what RFC 8259 actually requires from industry convention and OpenFormatter's own recommendations — so you know which rules you can bend and which you can't.
JSON RFC
JSON's specification has a real history: an original format, three successive IETF RFCs, and a parallel Ecma standard. Learn why each revision happened and which document to actually cite today.
JSON FAQ
Quick answers to specific JSON questions that don't need a full topic page — each one links to the reference page that covers it in depth.