What is JSON? The Complete Definition & Guide

JSON Definition

JSON stands for JavaScript Object Notation. It is a lightweight, text-based, language-independent data interchange format defined by IETF RFC 8259 and ECMA-404.

Despite its name, JSON is not limited to JavaScript — it is supported natively in every major programming language: Python, Java, C#, Go, Rust, PHP, Ruby, Swift, and more.

The 6 JSON Value Types

• Object ({ }): Unordered collection of key-value pairs. Keys must be strings.
• Array ([ ]): Ordered list of any JSON values.
• String: Double-quoted Unicode text.
• Number: Integer or floating-point. No NaN or Infinity.
• Boolean: Strictly lowercase true or false.
• Null: The absence of a value, written as lowercase null.

Brief History

JSON was created by Douglas Crockford in the early 2000s and first specified in 2006 (RFC 4627). The current standard is RFC 8259 (December 2017).

Common Use Cases

• REST API request and response payloads
• Configuration files (package.json, tsconfig.json, appsettings.json)
• NoSQL document storage (MongoDB, Firestore, DynamoDB)
• Web browser localStorage and sessionStorage
• Data exchange between microservices

// A valid JSON document demonstrating all 6 types:
{
  "name": "JSON2X",          // string
  "version": 2.8,            // number
  "isActive": true,          // boolean
  "deletedAt": null,         // null
  "tags": ["json", "tools"], // array
  "meta": {                  // object
    "author": "JSON2X Team",
    "license": "MIT"
  }
}