JSON — JavaScript Object Notation

Reference & Beautifier

{
  "name":        "Ada Lovelace",     // string
  "age":         36,                // number
  "active":      true,              // boolean
  "nickname":    null,              // null
  "scores":      [98, 100, 87],     // array
  "address":     {                  // object
    "city":      "London",
    "postcode":  "W1A 1AA"
  }
}

"key" — object key "string" — text 42 — number true/false — boolean null — nothing { } [ ] — structure

"string"

"hello world"

Any text, always wrapped in double quotes.

number

42 · -7 · 3.14

Integer or decimal. No quotes needed.

boolean

true · false

A yes/no flag. Always lowercase.

null

Represents the intentional absence of a value.

[array]

[1, "two", true]

An ordered list of any JSON values.

{object}

{"key": value}

A collection of key–value pairs. Keys must be strings.

1999

JavaScript Object Literals

JavaScript 1.0 (Netscape) includes object literal syntax — the direct precursor to JSON. Douglas Crockford recognizes it as a useful stand-alone data format.

2001

JSON Is Born

Douglas Crockford formalizes JSON and registers the domain json.org. The format is derived directly from JavaScript object literal notation and is designed to be minimal and human-readable.

2002

json.org Launched

Crockford publishes the canonical JSON specification at json.org with railroad diagrams describing the grammar. The page becomes the de facto reference for years.

2005

The Ajax Era Begins

Jesse James Garrett coins "Ajax" (Asynchronous JavaScript and XML). JSON quickly displaces XML as the preferred payload format due to its smaller size and direct mapping to JavaScript objects.

2006

RFC 4627 — First Official Standard

The IETF publishes RFC 4627, the first formal specification for JSON. It defines the MIME type application/json and establishes the core grammar — objects, arrays, strings, numbers, booleans, null.

2009

JSON Schema Draft 00

Kris Zyp publishes the first JSON Schema draft, enabling validation and documentation of JSON structures. It becomes the foundation of tools like OpenAPI / Swagger.

2012

JSON5 — Relaxed Superset

JSON5 is proposed, adding comments, trailing commas, unquoted keys, and single-quoted strings — features useful in config files. Used today by projects like Babel and VSCode's tsconfig.json.

2013

ECMA-404 & RFC 7159

Ecma International publishes ECMA-404, the first ISO-approved JSON standard. RFC 7159 simultaneously replaces RFC 4627, clarifying ambiguities around encoding and number precision.

2016

JSON Patch & JSON Pointer

RFC 6902 (JSON Patch) and RFC 6901 (JSON Pointer) are standardized, enabling precise surgical updates to JSON documents — widely used in REST APIs and HTTP PATCH operations.

2017

RFC 8259 — Current Standard

RFC 8259 replaces RFC 7159, mandating UTF-8 encoding and removing the BOM. This is the current authoritative IETF specification for JSON, paired with ECMA-404 2nd edition.

2020s

JSON Everywhere

JSON is the dominant data interchange format on the web. REST APIs, package managers (npm, cargo, composer), configuration files, NoSQL databases (MongoDB, CouchDB), and serverless platforms all rely on it as their native format.