JSON Validator – Find Syntax Errors Instantly
Validate JSON with detailed error messages — line numbers, column positions, and clear descriptions.
What is JSON Validation?
This free JSON validator checks any document against the official JSON grammar (RFC 8259) and reports the exact line and column of every syntax error — so you fix the problem instead of hunting for it. Validation runs instantly as you type: a valid document shows a clear success state, while broken input pinpoints the offending character. Because it is a client-side validator, your JSON is checked locally — no upload, no server, no logging. Your data never leaves your browser.
Why use this validator?
Precise error locations beat generic "invalid JSON" messages: the validator catches the classics — trailing commas, single-quoted strings, unquoted keys, missing brackets, and stray comments — and tells you exactly where each one sits. Pair it with the Repair tool to fix them automatically, or the Diff tool to find why two API responses don't match. Instant local checks make it safe to validate sensitive or proprietary payloads without exposing them to a third-party service.
How to use the validator.
- Paste your JSON into the editor above
- Click "Validate" or press Ctrl+Enter
- See the result — valid JSON shows a green checkmark, invalid JSON shows the exact error with line and column
- Fix and re-check, then send the clean document onward via "Open in"
Related JSON tools.
Once your JSON parses, these tools build on a valid document:
- JSON Repairrepair broken JSON automatically
- JSON Schema Validatorvalidate against a JSON Schema
- JSON Formatterformat your JSON once it's valid
- JSON Diffdiff two API responses
- JSON Minifierminify validated JSON for production
- JSON → YAMLconvert valid JSON to YAML
- JSON → CSVflatten a validated array to CSV
- JSON → TypeScriptgenerate TypeScript types from valid data
- JSON Path Finderquery validated data with JSONPath
FAQ.
What is a JSON validator?
A tool that checks JSON syntax against the standard grammar (RFC 8259) and reports any errors, so you know immediately whether a document can be parsed safely.
What JSON errors does it catch?
Missing commas, unmatched brackets, trailing commas, unquoted keys, single quotes instead of double quotes, invalid escape sequences, and more.
Where is my JSON processed?
Entirely in your browser with client-side JavaScript. Nothing is uploaded to a server, so even confidential data stays private.
Why does my JSON fail with "unexpected token"?
The usual causes are a trailing comma, a missing quote, a comment, or a misplaced bracket. The validator shows the exact line and column to check first.
What is the difference between validation and repair?
Validation only reports errors; repair automatically rewrites broken JSON into valid JSON and shows you what it changed. Use the validator to diagnose, the repair tool to fix.
Does it validate JSON Schema too?
This tool checks syntax only. To validate data structure against a schema (types, required fields, enums), use the JSON Schema Validator.
Looking for a different transformation? Explore thefull JSON toolkit— 11 free, private, in-browser tools that never upload your data.