JSON Formatter & Validator
About the JSON Formatter & Validator
Paste messy or minified JSON and get it validated and pretty-printed with clean indentation. If the JSON is invalid, you find out immediately instead of hunting for a missing comma by eye. It runs fully in the browser using the native JSON parser, so even large payloads and confidential data stay on your device.
This tool works in your browser: the files and text you use are processed on your device and are not uploaded.
How to use it
- Paste your JSON into the editor.
- Format it to apply consistent indentation, or validate to check for errors.
- Copy the cleaned-up output.
Frequently asked questions
How does the formatter validate my JSON?
It uses the browser’s built-in JSON parser (the same one JavaScript uses), so validation follows the official JSON standard exactly. If parsing throws an error, the JSON is not valid.
What are the most common JSON errors?
Trailing commas after the last item, single quotes instead of double quotes, unquoted keys, and missing commas or brackets. Strict JSON also disallows comments — remove them before validating.
Is there a difference between JSON and a JavaScript object?
Yes. JSON is a stricter text format: keys must be double-quoted strings, no trailing commas, no comments, and no functions or undefined. Valid JSON is a subset of JavaScript object literal syntax.
Can I format very large JSON files?
Yes, within your browser’s memory limits. Because everything is processed locally, formatting is fast and your data is never uploaded — though extremely large files may briefly hang the tab while parsing.