JSON Validator
Check whether JSON is valid and get the exact error position.
JSON Validator
Developer tool running locally in browser
What does JSON Validator do?
Validate JSON against the specification and get a precise diagnosis when it fails — line, column, the character that broke it and a plain-English explanation of what the parser expected instead.
How to Use JSON Validator
- 1Paste your JSONThe check runs as you type.
- 2Read the verdictValid, or the exact position and cause of the failure.
- 3Fix and re-checkThe error updates live as you edit.
Key Features
- Exact line and column for the first syntax error
- Plain-English explanation of what the parser expected
- Detects the classic mistakes: trailing commas, single quotes, unquoted keys, comments
- Structure summary when the JSON is valid
- Highlights the offending line in context
Frequently Asked Questions
What are the most common JSON errors?
A trailing comma after the last element, single quotes instead of double, keys without quotes, comments, and unescaped control characters or line breaks inside strings.
Does this validate against a JSON Schema?
No — it checks syntax only. Schema validation checks that the structure matches a contract and needs a schema document, which is a different job.
Why does my API reject JSON that validates here?
Syntactically valid JSON can still be semantically wrong: a missing required field, a string where a number belongs, or an unexpected extra property. Read the API error message for the specifics.
Can NaN or Infinity appear in JSON?
No. JSON only allows finite numbers. JavaScript serialises NaN and Infinity to null, which is a common source of surprise when a value silently disappears.
Input is processed in your browser and never transmitted. That said, treat any web page as untrusted for live production secrets — rotate anything you paste anywhere.
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