JSON Validator
Check whether a JSON document is valid and see exactly where it breaks.
Paste a document above. Nothing is sent anywhere — validation uses your browser's own JSON parser.
About JSON Validator
A validator answers one question quickly: is this document parseable JSON, and if not, where does it go wrong? Rather than guessing at an error such as "unexpected token", this tool maps the failure back to a line and column and shows the surrounding text.
It also reports useful statistics about a valid document - total keys, maximum nesting depth and size - which is handy when auditing an API response.
How JSON Validator works in your browser
Validation uses the browser’s native JSON parser, which follows ECMA-404 and RFC 8259 exactly. When a document fails, the parser’s error position is mapped back to a line and column and the surrounding text is shown, so you can see the character that broke it.
For a valid document the tool also reports total keys, maximum nesting depth and size. It checks syntax only — validating against a JSON Schema is a separate problem.
When to use it
- Finding the exact position of a trailing comma or missing quote in a config file.
- Confirming an API response is valid JSON before debugging your parser.
- Checking nesting depth and size when auditing a large payload.
Frequently asked questions
Which JSON specification is used?
The validator uses the browser native JSON parser, which implements ECMA-404 / RFC 8259. Trailing commas, comments and single quotes are rejected.
Does it validate against a schema?
No. It validates syntax only. JSON Schema validation is a different problem and is not covered by this tool.
What do the line and column mean?
They give the position of the first character the parser could not accept, counted from the start of your document.