Check whether text is valid JSON — double-quoted keys and string values, no trailing commas, every bracket and brace matched — and get the specific syntax error when it is not. Validation uses the browser's built-in JSON.parse(), so nothing is uploaded.
What does "valid JSON" mean?
Valid JSON follows a strict syntax: keys and string values must use double quotes (not single quotes), there can be no trailing commas after the last item, and every bracket and brace must be properly closed and matched. This tool checks your text against that syntax using the browser's built-in JSON.parse(), and if something's wrong, it tells you the specific error rather than leaving you to guess.
How to use the JSON Validator
- Paste — paste the JSON you want to check into the input box above. It doesn't matter whether it's an API response or a config file you wrote yourself.
- Validate — press the "Validate JSON" button and the syntax is checked instantly with
JSON.parse(). - Check the result — if the syntax is correct a success card appears; if there's a problem, an error card tells you what went wrong and where.
- Fix — correct the spot the error message points to, then validate again, repeating until it's valid.
What are common JSON errors?
The three most frequent are double-quote problems, trailing commas, and mismatched brackets. Wrapping a key or string in single quotes (') is an error in JSON — it must be double quotes ("). A comma (,) after the last item of an array or object isn't allowed either, and a mismatch between the number of opening and closing brackets or braces also fails. The error message in the validation result tells you where the problem occurred, so you can find and fix it quickly.
How is validating different from formatting?
Validation only answers "is this JSON syntactically correct?", telling you whether it passes and where any error is. Formatting (pretty-printing) re-arranges already-valid JSON with indentation and line breaks so it's easy to read, or conversely compresses it to a single line. Check that it's valid here first, then use the JSON Formatter to tidy it up.
When would I use this?
Useful when an API call is failing and you suspect the request or response body isn't valid JSON, when checking a config file you hand-edited, or before pasting JSON into a system that will reject it silently on a syntax error. If you also need to pretty-print or minify valid JSON, try the JSON Formatter.
Is my data safe?
Yes. All validation is handled inside your browser with JSON.parse() only, and the JSON you enter is never sent to or stored on any server. It works even without an internet connection, so you can safely paste and check sensitive data.