JSON Formatter & Validator
Pretty-print JSON, see the exact syntax error, and minify.
About JSON Formatter & Validator
Minified JSON coming back from an API is effectively unreadable; this tool indents it and, when the structure is broken, points to exactly where. The most common cause of invalid JSON is a trailing comma after the last array or object member — legal in JavaScript, but not in JSON.
How to use JSON Formatter & Validator
- 1
Paste your API response or JSON file contents into the input box.
- 2
Formatting happens instantly; if the structure is invalid you get an error message with the position.
- 3
Use the minify button to collapse it back down for transport.
- 4
Copy the result or paste it straight into your editor.
Frequently asked questions
Why is my JSON reported as invalid when it works in the browser?
It is probably a JavaScript object rather than JSON. JSON requires double-quoted keys, forbids trailing commas and does not accept single quotes.
Is my data stored anywhere?
No. Everything runs inside your browser and no request reaches our servers — you can disconnect from the internet and the tool still works.
Does it handle large files?
Yes, it stays responsive up to several megabytes. Beyond that, speed depends on your own device memory and CPU.