JSON Formatter & Beautifier
Format and validate JSON online. Runs entirely in your browser — nothing is uploaded. Precise line-and-column errors, duplicate-key warnings, and minify support.
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.