JSON Validator
Check your JSON for syntax errors instantly. Clear error messages help you fix issues fast — nothing ever leaves your browser.
This tool runs entirely in your browser. No data is ever sent to any server.
JSON Validation FAQ
What makes JSON valid?
Valid JSON must follow RFC 8259: strings in double quotes, no trailing commas, no comments, no single quotes, no undefined values, and proper nesting of objects and arrays. Numbers cannot have leading zeros.
What are common JSON errors?
The most frequent issues are: trailing commas after the last item, single quotes instead of double quotes, unquoted keys, comments (JSON does not support them), and missing commas between elements.
Can I validate JSON with comments?
Standard JSON (RFC 8259) does not allow comments. If your file uses JSONC (JSON with Comments) or JSON5, you will need to strip comments before validating. This tool validates strict JSON only.
Is this validator strict?
Yes. This tool uses the browser's native JSON.parse() which follows the JSON specification strictly. It will reject relaxed formats like trailing commas, single-quoted strings, and hexadecimal numbers.
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