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JSON Formatter & Beautifier

Format and validate JSON online, entirely in your browser. Precise line-and-column errors, duplicate-key warnings, and minify support.

Paste your JSON, choose an indentation, and click Format. Output is pretty-printed or minified entirely in your browser — nothing is uploaded.

Input
Formatted output

What this JSON formatter does

This JSON formatter and beautifier pretty-prints minified or messy JSON into readable, indented output, or minifies it back down when you need fewer bytes. Because everything runs in your browser, there is no upload, no account, and no copy of your data kept anywhere.

How it works

1. Parse. Your input is parsed with a strict, RFC 8259-compliant JSON parser. Anything that is not valid JSON — trailing commas, single quotes, unquoted keys, stray bytes — is rejected with an exact line and column.
2. Detect problems. Duplicate keys and very large integers are surfaced as warnings instead of being silently dropped, so you can fix them before shipping.
3. Re-serialize. The parsed value is written back out with your chosen indentation (2 or 4 spaces, or tabs), preserving key order and string escaping.
4. Done locally. The formatted result never touches a server.

Frequently asked questions

How do I format or pretty-print JSON?

Paste your JSON into the input pane and click Format. Choose 2 or 4 spaces, or tabs, for the indentation. The tool can also minify JSON when you need a smaller payload.

Can it detect errors in my JSON?

Yes. Invalid JSON is rejected with the exact line and column of the problem, and duplicate keys or very large integers are flagged as warnings instead of being silently dropped.

Does it work with large JSON files?

Yes. Formatting runs locally in your browser, so large documents work — though the browser's memory is the only practical limit.

Does JSON Formatter & Beautifier upload my data?

No. JSON Formatter & Beautifier runs entirely in your browser — your input never leaves this page.

Is JSON Formatter & Beautifier free to use?

Yes. JSON Formatter & Beautifier is completely free, with no account and nothing to sign up for.

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Updated 2026-08-07 · Runs in your browser — your data never leaves this page.