JSON Validator & Syntax Checker
Validate JSON syntax online for free. Instantly detect errors in your JSON with line/column error highlighting and detailed error messages.
Frequently Asked Questions
What makes JSON invalid?▾
Common causes of invalid JSON are: trailing commas (e.g. [1, 2, 3,]), single quotes instead of double quotes, comments (// or /* */), unquoted property names, NaN or Infinity values, undefined values, and mismatched brackets or braces.
How do I validate JSON online?▾
Paste your JSON into the text area on this page and click Validate. The tool instantly highlights errors with the exact line and column number. Green means valid, red means there are syntax errors.
What is the difference between JSON lint and JSON validation?▾
JSON lint and JSON validation are the same thing — both check if your JSON is syntactically correct according to the JSON specification (RFC 8259). Some linters also check style conventions on top of syntax validation.
Can JSON have comments?▾
No. Standard JSON does not support comments. If you need comments in a JSON-like format, use JSON5 or JSONC (JSON with Comments) which are supersets of JSON that allow // and /* */ style comments.
What is valid JSON?▾
Valid JSON must start with either an object {}, an array [], a string, a number, a boolean, or null. All string keys in objects must use double quotes. All string values must use double quotes. No trailing commas are allowed.