JSON Validator
This JSON validator checks your JSON against the official syntax rules and highlights the exact error line when something is wrong. Paste your JSON below — validation runs instantly in your browser with no data sent to any server.
What is a JSON Validator?
A JSON validator parses your JSON text against the RFC 8259 specification and reports whether it is valid. It checks for common mistakes such as missing commas, unquoted keys, trailing commas, mismatched brackets, and invalid escape sequences.
When validation fails, this tool highlights the exact line containing the syntax error and shows a descriptive message so you can fix the problem immediately without hunting through hundreds of lines manually.
Common JSON Syntax Errors
| Error | Example | Fix |
|---|---|---|
| Trailing comma | {"a": 1,} | Remove the final comma |
| Unquoted key | {a: 1} | Wrap key in double quotes: {"a": 1} |
| Single quotes | {'a': 1} | Use double quotes: {"a": 1} |
| Missing comma | {"a": 1 "b": 2} | Add comma: {"a": 1, "b": 2} |
| Undefined value | {"a": undefined} | Use null: {"a": null} |
Frequently Asked Questions
What JSON standard does this validator check against?
The validator uses the browser's native JSON.parse(), which conforms to RFC 8259 — the same standard used by virtually all JSON parsers in production environments.
Can I validate JSON with comments?
Standard JSON (RFC 8259) does not allow comments. If your file has // or /* */ comments, remove them first. Some tools use JSON5 or JSONC as extensions, but those are not valid JSON.
Is my JSON data sent to a server?
No. Validation runs entirely in your browser. Your data is never transmitted anywhere, which makes this safe for internal or confidential JSON.
What is the difference between a JSON validator and a JSON schema validator?
A JSON validator checks that text is syntactically valid JSON. A JSON schema validator also checks that the data matches a specific shape defined by a JSON Schema document. Use the JSON Schema Validator tool on this site for schema validation.
Why does valid JavaScript not always pass JSON validation?
JavaScript object literals allow unquoted keys, single quotes, trailing commas, and comments — none of which are allowed in JSON. JSON is a strict subset of JavaScript syntax.
How do I validate a large JSON file?
Paste the contents directly into the input box. Because processing is client-side, performance scales with your device. Files up to several megabytes validate in milliseconds on modern hardware.
Frequently Asked Questions
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