JSON Validator
Validate JSON syntax in real time. Instantly check for errors, find issues with line-level precision, and lint your JSON payloads.
JSON validator — check syntax in real time
A JSON validator ensures your JSON data is syntactically correct before you use it in your application. FormatList's free JSON validator checks your JSON in real time, highlighting errors with precise line and column numbers.
Why validate JSON?
- Find syntax errors before they break your app.
- Detect trailing commas, missing quotes, and bracket mismatches.
- Validate AI-generated JSON output for correctness.
- Check API payloads before sending them to production.
JSON validator FAQ
How does this JSON validator work?
It parses your JSON using JavaScript's built-in JSON parser. If parsing succeeds, your JSON is valid. If it fails, the error message shows exactly what's wrong and where.
What errors can it detect?
Common errors: trailing commas, missing commas, unescaped quotes, single quotes instead of double quotes, mismatched brackets, invalid numbers, and duplicate keys.
Can I use it to validate AI-generated JSON?
Yes. AI models sometimes produce invalid JSON. Paste the output here to catch and fix syntax issues before using it in your code.
Is validation done in real time?
Yes. Every keystroke triggers validation, so you see errors instantly as you type or paste.
Is my data sent to a server?
No. All validation happens locally in your browser. Your JSON never leaves your computer.
Related JSON tools
Format, validate, repair, compare, escape, and transform JSON with these browser-based tools.