Rollphy

Format and validate JSON

Pretty-print, minify and validate JSON right in your browser. Live error messages, no sign-up, nothing ever sent to a server.

Paste any JSON — an API response, a config file, a log line — and it’s formatted as you type. Pretty-print at 2 or 4 spaces, or minify it back down for transport. Everything runs locally in your tab: secrets, tokens and customer data in the payload never leave your device.

Invalid JSON gets the parser’s real error message, including the position where parsing stopped — usually all you need to spot the stray comma or missing quote.

The formatter accepts anything JSON.parse accepts (objects, arrays, strings, bare numbers) and rejects JSON5-style trailing commas, because the point of a validator is telling you what the strict parser on your server will think.

Frequently asked questions

Is my JSON sent to a server?
No. Formatting happens in your browser with the native JSON parser. API responses containing secrets or personal data never leave your machine.
Why does my JSON with trailing commas fail?
Trailing commas are invalid in standard JSON — some editors accept them (JSON5 style), but servers and languages parse strict JSON. That’s exactly what the validator simulates.
How large can the input be?
Several megabytes are fine. Everything runs in your tab, so the limit is your device’s memory, not a server’s quota.
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