JSON Formatter & Validator
Paste or upload JSON, validate it, beautify it with the indentation you prefer, or minify it in one click.
No heavy editor
This tool uses a plain <textarea>, not a full code editor (like Monaco) — it keeps the page light and fast to load, at the cost of no syntax highlighting inside the text box itself.
Privacy
The JSON is processed in your browser by JavaScript's own engine. It's never sent to Numelto or to any external service.
Common JSON validation errors
To convert to another format, use JSON to YAML or XML to JSON.
| Error | How to fix it |
|---|---|
| Trailing comma | Remove the last comma in objects and arrays |
| Single quotes | Use double quotes for keys and strings |
| Unquoted key | Wrap the key in double quotes |
| Comments | JSON doesn't support comments: remove them |
Formatting vs. minifying
Formatting adds indentation and line breaks so the JSON is readable by a person; minifying does the opposite, stripping every unnecessary space so the file is as small as possible when sent between systems.