Free Online JSON Formatter, Validator & Beautifier

Paste minified or messy JSON above and click Beautify to pretty-print it with 2-space, 4-space or tab indentation. Click Validate to check syntax and get the exact line and column of any error, or Minify to compress formatted JSON back to a single line for transport. Everything runs locally in your browser — your API responses, config files and payloads are never uploaded to any server.

Why format JSON?

APIs typically return JSON minified to save bandwidth: one enormous line with no spacing. That is efficient for machines and unreadable for humans. Pretty-printing restores indentation and line breaks so you can see the structure — which keys exist, how objects nest, where an array begins and ends. It is the fastest way to debug an unexpected API response or understand an unfamiliar payload.

Common JSON errors this validator catches

• Trailing commas — {"a": 1,} is invalid JSON, even though JavaScript allows it.
• Single quotes — JSON strings and keys must use double quotes: {'a': 1} fails.
• Unquoted keys — {a: 1} is a JavaScript object literal, not JSON.
• Missing brackets or braces — an unclosed [ or { somewhere deep in a large payload.
• Comments — standard JSON does not allow // or /* */ comments at all.
• Invalid values — undefined, NaN and functions cannot appear in JSON.

When validation fails, the error message includes the line number so you can jump straight to the problem. For a deeper walkthrough see our guide to fixing "Unexpected token" JSON errors.

Is it safe to paste sensitive JSON here?

Yes. This tool performs 100% of its processing client-side using your browser's built-in JSON.parse and JSON.stringify. Nothing is transmitted, logged or stored — you can disconnect from the internet after the page loads and it keeps working. That makes it appropriate for config files and internal payloads that should never touch a third-party server.

Frequently asked questions

What is the difference between beautify and minify?

Beautify adds indentation and line breaks for humans; minify removes all unnecessary whitespace for machines. Both produce semantically identical JSON.

Is there a size limit?

Only your browser's memory — multi-megabyte payloads format in well under a second on a modern machine.

Does it reorder my keys?

No. Key order is preserved exactly as it appears in your input.

Can it fix invalid JSON automatically?

It pinpoints the error but does not silently rewrite your data — automatic "fixing" can corrupt meaning. Correct the reported line, then re-validate.