How to use the JSON Validator
- Paste your JSON or open a file.
- Read the result: “Valid JSON”, or the exact line and column of the first error with an explanation.
- Fix the error and the check updates instantly.
What makes JSON valid
- Strings and object keys use double quotes.
- Values are strings, numbers, true, false, null, objects or arrays.
- Items are separated by commas, with no comma after the last item.
- No comments, no trailing commas, no
undefined.
The most common JSON errors
- Trailing comma — common when copying from JavaScript objects.
- Single quotes — Python dictionaries printed with
print()use them. - Missing comma between two properties after editing by hand.
- Unescaped characters inside strings, such as a raw line break or a backslash in a Windows path.
- Truncated output — a log line or API response cut off before the closing brackets.
Validation vs schema validation
This tool checks syntax: whether the text is JSON at all. It doesn't check that the data has the fields your application expects — that's what JSON Schema is for. To read and explore valid JSON, use the JSON viewer.
Frequently asked questions
Why does my JSON work in JavaScript but fail here?
JavaScript object literals are more permissive than JSON: they allow single quotes, unquoted keys, trailing commas and comments. JSON.parse — and every API — follows the stricter JSON standard.
Is my data sent anywhere?
No. Validation uses your browser's own JSON parser and nothing leaves your device.