What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based data format used to exchange structured data between systems. It originated in JavaScript but is now language-independent and supported by virtually every modern programming language.

A JSON document is built from a small set of building blocks:

Objects: unordered collections of key-value pairs wrapped in {}
Arrays: ordered lists of values wrapped in []
Primitives: strings, numbers, booleans, and null

Here is a minimal example representing a single user record:

{
  "id": 42,
  "name": "Ada Lovelace",
  "active": true
}

The core value types and their typical use cases are summarized below.

Type	Example	Typical use
`string`	`"hello"`	Names, labels, free text
`number`	`3.14`	IDs, counts, measurements
`boolean`	`true`	Flags, feature toggles

JSON is widely used for REST API payloads, configuration files, and persisting application state because it is easy to read, easy to parse, and supported everywhere.