How to validate JSON syntax and find errors

A single missing comma, an extra bracket, or a trailing comma turns valid JSON into an unresolvable parse error. Tracking down the error by eye in a 500-line JSON file is painful. The quickhelp.dev JSON Formatter validates any JSON string instantly, reports whether it's valid, and — if it isn't — shows the exact line and column of the first error. The optional Repair mode can automatically fix the most common issues.

Step-by-step guide

1. Paste the suspect JSON: Copy the JSON you want to validate and paste it into quickhelp.dev/json-formatter.
2. Check the result: If the JSON is valid, the formatted output appears. If it's invalid, a red error message shows the problem and its exact line:column position.
3. Fix or repair: Correct the error manually based on the line number, or enable 'Repair' mode to automatically remove trailing commas, fix single-quoted strings, and strip comments.

Frequently asked questions

What errors can Repair mode fix automatically?

Trailing commas before } or ], single-quoted strings, bare (unquoted) object keys, and JavaScript-style // and /* */ comments.

Is there a file size limit for validation?

The API endpoint accepts up to 1 MB. For larger files, validate locally with: node -e "JSON.parse(require('fs').readFileSync('file.json','utf8'))"