JSON Validator & Formatter

Free · no signup · runs entirely in your browser

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This tool checks whether your JSON is valid and, if it is, formats it into something a human can actually read. Paste in a wall of minified JSON, hit the button, and get back a properly indented version — or a clear message telling you where the syntax broke. It's free, no signup, and it doesn't nag you to upgrade.

The useful part is the error reporting. When JSON is malformed — a trailing comma, a missing quote, a bracket that never closed — the tool tells you it's invalid and points at the problem instead of just failing silently. If you've ever stared at a config file wondering why your app won't start, you know that a good error message is worth more than a pretty one. This handles both: it validates first, then formats what passes.

Everything runs in your browser. Your JSON is parsed locally in JavaScript and never uploaded, which matters if you're pasting in an API response, a config file, or anything with keys and tokens you'd rather not hand to a random website. There's no server logging your payloads because there's no server involved. Paste sensitive data, get your answer, close the tab — nothing lingers, nothing gets stored.

How to use it

  1. Paste your JSON into the input area.
  2. Run the check — the tool validates it and flags any syntax error, or confirms it's valid.
  3. Read the pretty-printed, indented output and copy it back out.

Worked example

Imagine an API returned a single unreadable line: {"user":{"id":42,"roles":["admin","editor"],"active":true}}. You paste it in, and the tool confirms it's valid and re-prints it with proper indentation and line breaks, so you can actually see the nested roles array at a glance. If instead you'd pasted a version with a stray trailing comma, it would tell you the JSON is invalid and where the parser choked, saving you a slow manual hunt through the braces.

FAQ

What's the difference between validating and formatting JSON?

Validating checks that the JSON is syntactically correct — no missing brackets, quotes, or stray commas. Formatting (pretty-printing) takes valid JSON and re-indents it so it's readable. This tool does both.

Will it tell me where my JSON is broken?

Yes. When the JSON is invalid, it reports the syntax error rather than failing silently, so you can find and fix the problem faster than scanning by eye.

Is my JSON sent to a server?

No. Parsing happens entirely in your browser with JavaScript, so your data never leaves your device. Nothing is uploaded or stored, which is handy for API responses or config with sensitive values.

Do I need an account to use it?

No account, no signup, no cost. Paste your JSON, check it, and go — there are no limits on how often you can use it.

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