Free JSON Formatter & Validator Online
Paste your JSON below. Validation and formatting happen automatically.
JSON is the most common format for exchanging data between systems — it's what most AI APIs return, for example. One extra comma or an unclosed bracket is enough to break it, and the browser's native error message isn't always easy to understand.
Validation follows the official JSON standard (RFC 8259). All processing happens in your browser — nothing is sent to any server.
Frequently asked questions
What does "minifying" a JSON mean?
It's removing all the spaces and line breaks that only exist to make it easier for humans to read, making the file smaller — useful for sending to an API or storing with less space.
Why is my JSON showing an error if it looks correct?
The most common issues are a trailing comma after the last item in a list or object, single quotes instead of double quotes, or an unclosed bracket. JSON is quite strict about these details.
Does this tool send my JSON to a server?
No. All validation and formatting happens in your own browser — the pasted text never leaves your computer.
Does it work with large JSON files?
Yes, the practical limit is your browser's memory, not the tool itself. JSON files of a few megabytes work without any issue.