About the JSON Validator
Invalid JSON is one of the most common and frustrating sources of bugs when integrating APIs or loading configuration. A single trailing comma, a smart quote pasted from a document, or an unescaped newline inside a string is enough to break parsing entirely. This validator parses your input with the same strict rules a server or library would use, and reports precisely where the document stops being valid.
Unlike a formatter, the validator focuses on diagnostics: it tells you whether the document conforms to the JSON specification and, when it does not, surfaces the error message along with the line and column so you can jump straight to the problem. Because validation runs locally, it is instant and private, making it safe to check production payloads, secrets or customer data without sending anything over the network.
How to use the JSON Validator
- 1Paste or type the JSON you want to check into the editor.
- 2The validation result updates live as you type.
- 3If the JSON is invalid, read the error message and the highlighted line and column.
- 4Fix the reported issue and watch the status turn green when the document becomes valid.
Key benefits
- Real-time validation as you type.
- Precise line and column for the first error.
- Strict, specification-compliant parsing.
- Completely private — runs in your browser.
- Handles deeply nested and very large documents.
Real-world examples
Debug a failing API call
Paste the response body to confirm whether malformed JSON is the cause.
Lint a config before committing
Catch typos in tsconfig.json or a CI config before they break a build.
Verify generated JSON
Confirm that JSON produced by a script or template is well-formed.
Frequently asked questions
What makes JSON invalid?+
Common causes include trailing commas, single quotes, unquoted keys, comments, and unescaped control characters inside strings. None of these are allowed by the JSON specification.
Does the validator check against a schema?+
This tool validates syntax (is it well-formed JSON?). Schema validation against JSON Schema is a separate concern that we may add as a dedicated tool.
Is my JSON sent anywhere?+
No. Validation is performed entirely in your browser; nothing is uploaded.
Why does it say my number is invalid?+
JSON does not allow leading zeros, hexadecimal numbers, NaN, Infinity, or a trailing decimal point. Use plain decimal notation.