Is JSON the same as a JavaScript object?

They look similar, but JSON is a text format with stricter rules. JSON keys must be quoted strings, it allows no comments or trailing commas, and it supports only a fixed set of value types.

Can JSON store dates?

JSON has no native date type. Dates are usually stored as strings, most often in ISO 8601 format such as 2026-06-25T12:00:00Z, and parsed by the receiving code.

Does this send my data anywhere?

No. Utilumo's developer tools parse and transform input inside the browser tab. Nothing is uploaded, stored, or logged.

Explainer1 min readUpdated June 25, 2026

What is JSON?

Short answer

JSON (JavaScript Object Notation) is a lightweight, text-based data format used to store and exchange structured data. It is human-readable, language-independent, and is the most common format for web APIs.

What JSON looks like

JSON represents data as key/value pairs inside objects, and ordered values inside arrays. Despite the name, it is not tied to JavaScript: nearly every language can read and write it.

{
  "name": "Ada Lovelace",
  "active": true,
  "roles": ["author", "mathematician"],
  "score": 99.5,
  "manager": null
}

A small JSON object

The data types

String, written in double quotes
Number, integer or decimal
Boolean, true or false
null, the empty value
Object, an unordered set of key/value pairs in braces
Array, an ordered list of values in brackets

Rules people forget

Keys must be strings wrapped in double quotes. Single quotes are not valid JSON.
No trailing commas after the last item in an object or array.
No comments. JSON has no syntax for them.
The format is strict: a single missing brace or quote makes the whole document invalid.

JSON is a standardJSON is defined by RFC 8259 and ECMA-404. Its media type is application/json.

Try it: JSON FormatterPaste JSON to format, validate, and find the exact line of a syntax error.Open tool

Where JSON is used

JSON is the default payload for REST APIs, configuration files, log lines, and data exchange between services. Because it maps cleanly onto objects and arrays, most languages can parse it into native data structures in one call.