Pretty JSON — Validator & Formatter
Free tool for validating, repairing, and formatting JSON. Works locally in your browser — privately and securely.
Paste your JSON, fix errors with one click, and format it for readability. Everything happens in your browser — no data is sent to any server.
Paste JSON in the left panel
100% private — processing happens locally in your browser
- Copy your JSON (from logs, API, config files) and paste it in the left panel. Validation happens automatically.
- If your JSON has syntax errors (trailing commas, single quotes, missing commas), you'll see a list with their locations.
- Click "Fix All" to automatically repair common issues. The tool uses the jsonrepair library.
- After fixing, click "Format", then copy the result to clipboard or download as a .json file.
Privacy: Your JSON never leaves the browser. All processing happens locally.
Is my data sent to a server?
No. All JSON processing (validation, repair, formatting) happens 100% locally in your browser. Your data never leaves your device.
What JSON errors can be fixed?
The tool automatically fixes: trailing commas, single quotes instead of double, missing commas between elements, unclosed brackets and quotes, and many other common issues.
Can I format very large JSON?
Yes, but performance depends on your browser. For files over 1MB there may be a brief delay. For very large files (10MB+) we recommend desktop tools.
Does the tool support JSON5 or JSONC?
The tool validates against strict JSON standard. Comments and JSON5 extensions will be reported as errors, but can be auto-fixed.
What if repair doesn't help?
Some errors require manual intervention (e.g., missing values, improperly nested structures). In that case, the error list shows the exact location of the problem.