JSON Formatter & Validator

No. Parsing, formatting, and minifying all run in JavaScript inside your browser tab. Pasted text and uploaded files never leave your machine, so the tool is safe for API responses that contain tokens or customer data. Loading from a URL is the one exception: your browser requests that URL directly, and nothing goes through our servers.

Formatting (beautifying) adds line breaks and indentation so a human can read the structure. Minifying removes all insignificant whitespace, which gives the smallest payload for sending over the network or storing in a config value. Both keep the data exactly the same.

JSON is stricter than JavaScript object syntax. The most common causes are trailing commas, single-quoted strings, unquoted keys, comments, and values such as undefined, NaN, or Infinity. None of these are allowed in JSON (RFC 8259). LLM output often contains them too, so validating model responses before you parse them in code is a good habit.

Browsers only let a page read a response from another site if that server sends CORS headers allowing it. Many public APIs and raw file hosts do, but plenty don't. If a URL fails, open it in a new tab, save the response as a file, and upload it instead.

Uploads are capped at 10 MB. Past a few thousand lines, the output switches from syntax highlighting to plain text so the page stays responsive. For multi-megabyte documents, turn off Auto update so the tool only re-parses when you click a button.