JSON Formatter & Validator
Paste JSON to pretty-print it, minify it, or find exactly where it’s broken. Everything runs in your browser. Nothing you paste is uploaded or stored.
Quick answer
Paste JSON to pretty-print it, minify it or find the exact line and column of a syntax error. Everything runs in your browser, so API responses and config files are never uploaded.
- Free
- No sign-up
- Developer
- Updated October 2026
About the JSON Formatter & Validator
API responses and config files are often a single unreadable line. Formatting adds indentation and line breaks so you can see the structure; minifying does the opposite for smaller payloads.
Validation uses the browser’s own strict JSON parser, so if it passes here it will parse in any standards-compliant language. Common mistakes it catches: trailing commas, single quotes, unquoted keys, comments and stray characters.
How to use it
- Paste your JSON on the left.
- Choose Format or Minify and your indentation.
- Tick “Sort keys” to order object keys alphabetically — handy for comparing two payloads.
- Copy the result.
Worked example
Fixing a common error
- Input: {"a": 1, "b": 2,} — note the trailing comma.
- The validator reports an unexpected token and its position.
- Remove the comma and the JSON validates.
Frequently asked questions
Is my JSON sent to a server?
No. Parsing and formatting happen entirely in your browser, so it’s safe for API keys, tokens or customer data — though you should still avoid pasting secrets into any website you don’t trust.
Why is my JSON invalid when it works in JavaScript?
JavaScript object literals allow single quotes, unquoted keys, trailing commas and comments. Strict JSON allows none of those.
How large a file can I format?
Several megabytes work fine on a modern computer. Very large files may make the page slow because everything is processed locally.
Results are estimates for planning — check critical figures with a professional or the official source.
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