JSON Validator
Validate JSON online and pinpoint the exact syntax error, instantly.
Paste JSON and find out immediately whether it's valid — and if it isn't, exactly where the syntax breaks, down to the character position. No upload, no account, no size limit tied to a server request.
How to use JSON Validator
- 1Enter your input for json validator.
- 2Review the result on this page.
- 3Download or copy your result.
What validation catches that formatting doesn't
Valid-looking JSON often has a single small mistake — a trailing comma after the last item in an object, mismatched brackets, an unquoted key, or a stray comment (JSON doesn't support comments, unlike JavaScript) — that breaks parsing everywhere it's used: your app crashes, an API call fails, or a config file silently doesn't load. These errors are easy to introduce by hand-editing JSON and surprisingly hard to spot by eye in a large file.
A formatter will simply fail on broken JSON without necessarily telling you why; a validator's whole job is pinpointing exactly where the syntax breaks so you can fix it in seconds instead of scanning the file manually.
How this tool works
Paste your JSON and it's parsed entirely in your browser — nothing is uploaded. Valid JSON is confirmed immediately; invalid JSON returns the exact parser error, including the position where parsing failed, so you can jump straight to the problem instead of re-reading the whole file.
Once your JSON validates successfully, JSON Formatter re-indents it for readability — the two tools are meant to be used together: validate first, then format.
Common JSON errors this catches
The most frequent ones: a trailing comma after the last item in an object or array (JSON, unlike JavaScript, doesn't allow this), single quotes instead of double quotes around strings and keys, an unquoted object key, a missing comma between items, and mismatched or missing closing brackets. Each produces a specific parser error pointing at roughly where the problem is.
Frequently Asked Questions
How do I validate JSON online?
Paste your JSON into the box above — it's checked automatically, and any syntax error is reported with its location.
What's the most common JSON syntax error?
A trailing comma after the last item in an object or array — valid in JavaScript object literals, but not allowed in strict JSON, and one of the easiest mistakes to introduce by hand.
Can JSON have comments?
No — the JSON specification doesn't support comments (// or /* */). A file with comments will fail validation even if everything else is correctly formatted.
Is my JSON sent to a server?
No — validation runs entirely in your browser. Nothing you paste here is ever uploaded.
Is this tool really free?
Yes, JSON Validator is completely free to use — no sign-up, no hidden charges.