JSON

Also known as: JavaScript Object Notation, RFC 8259 JSON

JSON (JavaScript Object Notation) is a lightweight text format for structured data — built from objects, arrays, strings, numbers, booleans, and null — that's become the lingua franca of web APIs, configuration files, and data interchange between services.

Overview

JSON is defined by RFC 8259. The grammar is small: an object is a comma-separated list of string keys mapped to values inside curly braces; an array is a comma-separated list of values inside square brackets; values are strings (double-quoted), numbers (no leading zero, no NaN, no Infinity), 'true', 'false', or 'null'.

The strictness matters. Comments are not allowed. Trailing commas are not allowed. Keys must be quoted. Single quotes are not allowed. JavaScript object literals are NOT valid JSON. Always validate with a parser before assuming a payload is JSON.

JSON is human-readable but verbose. Binary alternatives like CBOR, MessagePack, and Protocol Buffers compress better when payload size matters, at the cost of needing a special decoder.

Common questions about JSON

Is JavaScript syntax valid JSON?

No. JavaScript object literals allow trailing commas, single quotes, unquoted keys, comments, and special values like Infinity and undefined — none of which are valid JSON. Parse with JSON.parse to enforce the spec.

Can JSON represent dates?

Not natively — JSON has no date type. The conventional workaround is to encode dates as ISO 8601 strings (e.g. '2026-06-14T22:30:00Z') and parse them on the receiving end.

Is JSON a strict subset of JavaScript?

Almost — but not quite. JSON allows two characters (U+2028 LINE SEPARATOR, U+2029 PARAGRAPH SEPARATOR) inside strings that older JavaScript engines could not eval cleanly. Modern engines handle them correctly.

Tools that work with JSON

JSON Formatter

Format, validate and minify JSON entirely in your browser.

JSON to Table Viewer

Render any JSON payload as a sortable, searchable HTML table.

CSV ↔ JSON Converter

Convert between CSV and JSON without uploading the file anywhere.

Base64
Base64 is a way of encoding arbitrary binary data as a string of 64 ASCII characters (A–Z, a–z, 0–9, '+', '/') so it can travel through systems that only handle plain text — like email, URLs, JSON, or HTML data URIs.