Free JSON Validator Online
Check whether your JSON is valid in one click. Get pinpoint error messages with line and column numbers — all inside your browser.
How it works
Paste your JSON
Paste the JSON you want to validate into the input panel.
Click Validate
The validator runs JSON.parse() and reports success or the exact error.
Fix errors
Use the error message and position to locate and fix the problem.
Zero uploads
Your JSON is validated entirely in your browser — never transmitted anywhere.
Common use cases
Pre-commit JSON checks
Validate config files (package.json, tsconfig.json, .eslintrc) before committing to ensure CI/CD doesn't break.
API request debugging
Confirm your request body JSON is syntactically correct before sending it to an endpoint.
Generated JSON verification
Validate JSON output from code generators, scripts, or AI tools before using it in production.
Learning JSON syntax
Understand exactly what constitutes a syntax error and why — great for beginners and documentation.
Frequently asked questions
What makes JSON invalid?
Common issues: trailing commas, unquoted keys, single-quoted strings, missing commas between items, and unclosed brackets or braces.
Does it validate JSON Schema?
No — this tool validates JSON syntax only (RFC 8259). For JSON Schema validation you need a separate schema validator.
Is the validator strict?
Yes — it uses the native JSON.parse() which follows the JSON spec exactly. Trailing commas and comments will fail.
Does my data leave my browser?
Never. Validation runs locally using the browser's built-in JSON.parse(). Your data stays on your device.
Can I validate large files?
Yes. Browser memory is the only limit. Multi-megabyte JSON files validate in milliseconds.
How do I get a line number for the error?
The error message from JSON.parse() includes the position. The validator also displays a character-count indicator to help locate it.