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JSON Formatter & Validator

Format, beautify, validate and minify JSON online. Find syntax errors and copy clean, readable JSON instantly.

How to use this tool

Steps for using the JSON Formatter.

  1. Paste your JSON into the Input JSON panel, click Load JSON data to fetch it from a URL, or click Load Example.
  2. Choose an indentation style — 2 spaces, 4 spaces or tabs — and optionally sort keys alphabetically.
  3. Click Format to pretty-print the JSON, or Minify to validate it and collapse it onto a single line.
  4. If the JSON is invalid, read the error banner: it shows the line, column and a caret pointing at the problem.
  5. Switch to the Tree View tab to expand and collapse nested objects, then Copy or Download the result.

Example

Pretty-print a minified API response

Minified JSON
{"id":1,"title":"Example","tags":["api","json"],"completed":false}
Formatted JSON (2 spaces)
{
  "id": 1,
  "title": "Example",
  "tags": [
    "api",
    "json"
  ],
  "completed": false
}

Common use cases

  • Reading a single-line API response copied from browser DevTools or a log file.
  • Finding the missing comma or unescaped quote that makes a config file fail to load.
  • Normalising indentation and key order before committing JSON fixtures to Git.
  • Exploring deeply nested payloads with the collapsible tree view.
  • Preparing readable JSON examples for documentation and bug reports.

How JSON formatting works

Formatting is a two-step process. First the text is parsed into a data structure — objects, arrays, strings, numbers, booleans and null. If parsing succeeds, the structure is serialised back to text with consistent indentation and one property per line. Because the output is generated from the parsed value, formatting can never change your data, only its whitespace.

Parsing uses your browser's native JSON.parse, the same engine your JavaScript code uses, so a document that formats here will also parse in your application. When parsing fails, a strict RFC 8259 scanner re-reads the input to report a precise line and column with a human-readable message — browsers otherwise word these errors differently or omit the position entirely.

Sorting keys is applied recursively to every object, which makes two documents with the same data but different key order produce identical output. That is useful before committing JSON fixtures or comparing documents in a diff. Array order is always preserved because it is meaningful in JSON.

Large integers beyond Number.MAX_SAFE_INTEGER (2^53 − 1) lose precision in any JavaScript-based parser, including this one. If you work with 64-bit IDs, keep them as strings in your JSON.

Limitations

  • Strict JSON only: comments, trailing commas and single-quoted strings are reported as errors.
  • Numbers larger than 2^53 − 1 lose precision, as in all JavaScript JSON parsers.
  • Input is limited to 2 million characters to keep the page responsive.

Frequently asked questions

Is my JSON sent to a server?

No. Formatting, validation and the tree view all run in your browser. The JSON you paste is not uploaded, logged or sent to analytics. If you use Load JSON data, your browser requests that URL directly — the request does not pass through our servers and no cookies are sent.

What is the difference between Format and Validate?

Both parse the input and report errors. Format also writes pretty-printed JSON to the output panel; Validate only confirms whether the input is valid without changing the output. For duplicate-key detection and structure statistics, use the JSON Validator.

Can I validate large JSON files?

Yes, up to about 2 million characters. Very large documents format quickly, but the tree view only renders the first 500 children of each node to stay responsive.

Does this tool support JSON5 or JSONC?

No. It follows standard JSON as defined in RFC 8259, which is what APIs and JSON.parse accept. Remove comments and trailing commas before formatting.

Why does Load JSON data fail for some URLs?

The URL is fetched by your browser, so the server must allow cross-origin requests (CORS) and use HTTPS. Many public APIs do; private or internal endpoints often don't. Responses are limited to 5 MB. If loading fails, open the URL in a new tab and paste the response instead.

Does Minify change my numbers or strings?

No. Minify validates the JSON and then removes only the spaces, tabs and line breaks between tokens. Values stay exactly as written — 1.0 stays 1.0, large 64-bit IDs keep every digit, and whitespace inside strings is preserved.

Is this JSON formatter free?

Yes. It is free to use with no sign-up and no usage limits beyond the input size cap.