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JSON Validator

Check whether your JSON is valid and get the exact line, column and cause of any syntax error.

Runs in your browser. Nothing you type is sent to a server.

How to use JSON Validator — Check JSON Syntax Online Free

  1. 1Paste your JSON into the left-hand box.
  2. 2A valid or invalid verdict appears immediately, with the failing line and column if there is a problem.
  3. 3Copy the result, or download it as a file.

About JSON Validator

JSON's rules are stricter than they look, and the differences from JavaScript object syntax catch people out constantly: keys must be double-quoted, strings cannot use single quotes, and a trailing comma after the last element is an error rather than a harmless habit.

This validator parses the document with the browser's own JSON parser — the same one your code will use — so a pass here means a pass in production. When it fails, the character offset is converted into a line and column and the failing line is printed, which is usually enough to spot the problem immediately.

If you are debugging an API, paste the raw response body rather than what a viewer shows you. A surprising share of "invalid JSON" reports turn out to be an HTML error page being returned where JSON was expected.

Frequently asked questions

What makes JSON invalid?
Trailing commas, single quotes instead of double quotes, unquoted keys, comments, NaN or Infinity, and unescaped control characters inside strings. All of these are legal in JavaScript but not in JSON.
Does it validate against a schema?
No — this checks syntax, not structure. It confirms the document parses as JSON; it does not check that a particular field exists or has a given type.
Can I validate JSON with comments?
Comments are not part of the JSON standard, so a document containing them is reported invalid. Formats like JSONC and JSON5 allow them, but standard parsers will reject the file.
Why does my API response fail validation?
Often the response is not JSON at all — an error page, an HTML redirect, or a JSON body wrapped in extra text. Paste the raw body and the error message usually makes the cause obvious.
Is my data sent to a server?
No. The whole tool is JavaScript running on your own device, so your text never leaves the browser. You can load the page, go offline, and it still works.
Is it free?
Yes — unlimited use, no sign-up, no watermark and no limit on how many times you run it.