JSON Formatter

What is JSON?

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 the default format for most web APIs, configuration files, and NoSQL databases.

JSON is built from two core structures: objects, which are unordered collections of "key": value pairs wrapped in curly braces { }, and arrays, which are ordered lists of values wrapped in square brackets [ ]. Keys must always be double-quoted strings.

JSON supports a small, strict set of value types: string (double-quoted), number (integer or floating point), boolean (true / false), null, plus nested objects and arrays. Comments, trailing commas, and single quotes are not permitted by the specification.

A JSON formatter takes raw or minified JSON and re-indents it into a clean, readable structure, while a validator checks it against the JSON standard (RFC 8259 / ECMA-404). Common uses include debugging API responses, inspecting log payloads, cleaning up configuration, and preparing data for documentation.

How to format JSON online

1. Paste your JSON into the editor, or click Upload to load a .json file (or Sample to try example data).
2. Click Format to pretty-print and indent the JSON, or choose Minify to compress it onto a single line.
3. Click Validate to check the JSON against the standard — errors are reported with the exact line and column.
4. Use the Indent control to switch between 2 spaces, 4 spaces, or Tab, and open Tree view to explore the data as a collapsible structure.
5. Click Copy to copy the result or Download to save it as a file; use Clear to start over.

JSON example: before & after

The formatter expanded the minified JSON onto multiple lines with 2-space indentation, preserving the original key order.

Before

{"id":42,"name":"Ada","roles":["admin","editor"],"active":true,"profile":{"city":"Berlin","verified":false}}

After

{
  "id": 42,
  "name": "Ada",
  "roles": [
    "admin",
    "editor"
  ],
  "active": true,
  "profile": {
    "city": "Berlin",
    "verified": false
  }
}

Formatter vs beautifier vs validator vs minifier

These terms overlap but describe different actions on your JSON:

• JSON Formatter / Beautifier: Re-indents and spaces out JSON so it is easy for humans to read. "Pretty-print JSON" means the same thing — adding line breaks and indentation (2 spaces, 4 spaces, or a tab).
• JSON Validator / Lint: Checks whether your text is valid JSON per the standard and reports exactly where it breaks (line and column), without changing the data.
• JSON Minifier: Does the opposite of beautifying — it removes all non-essential whitespace to produce the most compact valid JSON for storage or transmission.
• JSON Viewer: Renders the data as a navigable, collapsible tree so you can inspect deeply nested structures without scrolling through raw text.

Formatly combines all four in a single, private, client-side tool.

Common JSON errors and how to fix them

• Trailing comma after the last item in an object or array, e.g. [1, 2, 3,] Remove the comma that follows the final element or property.
• Single quotes used for strings or keys, e.g. {'name': 'Ada'} Use double quotes for all keys and string values: {"name": "Ada"}.
• Unquoted object keys, e.g. {name: "Ada"} Wrap every key in double quotes: {"name": "Ada"}.
• Missing comma between two values or properties Add a comma to separate each array element and each key/value pair.
• Comments included in the JSON (// or /* */) Remove all comments — JSON does not support them; move notes outside the data.
• Unescaped special characters or unterminated string Close every string with a matching double quote and escape characters like \" and \\ inside strings.

Private by design

Every byte of JSON you paste is processed locally in your browser. Formatly makes no network request with your data, logs nothing, and stores nothing on any server — so it is safe for API responses, configuration, tokens and other sensitive content. Your most recent input and theme are saved only in your own browser's local storage.

JSON Formatter FAQ

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