JSON Validator
Check JSON syntax and get the exact line and column of any error.
Nothing checked yet
Paste JSON and press Validate. You will get either a structural summary or the exact position of the first syntax error.
Runs entirely in your browser. Your data isn't uploaded — this page makes no network request with anything you type, which you can verify in your browser's network tab. How this works.
What is the JSON Validator?
A JSON validator answers one question precisely: is this document valid JSON, and if not, exactly where does it break? Most "invalid JSON" errors in the wild are a missing comma, a smart quote pasted from a document, or a trailing comma left behind after deleting a field.
Rather than just saying no, this validator reports the line and column, shows the offending region in context, and summarises the document you did get: depth, key count, array sizes and duplicate keys — the things that usually explain why a downstream parser behaved oddly.
How to use it
- Paste the JSON you want to check, or upload a file.
- Press Validate (or Ctrl/Cmd + Enter).
- If it is invalid, read the error line and column, and use the highlighted marker in the editor to jump straight to the problem.
- If it is valid, review the structure summary for duplicate keys and unexpected nesting depth.
Example
A trailing comma is the most common cause of invalid JSON.
{
"retries": 3,
"timeout": 30,
}
Invalid JSON Line 3, column 3 Unexpected token } — a value was expected after the comma on line 2.
Features
- Exact line, column and character offset for syntax errors
- Inline error markers in the editor
- Duplicate key detection (valid JSON, but usually a bug)
- Structure summary: type, depth, key and node counts
- Detects common paste damage such as curly quotes and non-breaking spaces