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JSON Validator

Validate JSON data and find syntax errors.

How to Use JSON Validator

1

Paste the JSON payload, request body, or config file contents into the validator box.

2

Click the "Process" button to run the check against the strict JSON grammar.

3

If it fails, read the reported line and column, fix that spot in your source, and validate again.

4

Once it reports valid JSON, copy the payload into your editor or your API client of choice.

Features

Reports the exact line and column where parsing failed
Catches the usual offenders: trailing commas, single quotes, unquoted keys
Rejects JSON5 extras such as comments, NaN, and Infinity in strict mode
Works on single fragments, full API responses, and large config files
Instant browser-based feedback with no upload and no account needed
Clear pass or fail confirmation you can screenshot into a ticket

Frequently Asked Questions

Yes, it is free with no sign-up and no usage limits. You can run as many checks as you like, which makes it convenient for validating a whole batch of fixtures while you work.
Many languages and frameworks parse relaxed variants such as comments, unquoted keys, single quotes, or NaN even though the JSON specification forbids them. If another service consumes your payload with a strict parser, it is worth validating here first and removing those extras.
No. The parse runs locally in your browser, so API keys, personal data, and internal payloads are never sent to us. Nothing is written to a database or an access log.
There is no meaningful limit for typical API payloads, and multi-megabyte documents validate fine. Extremely large files may take a second or two in the browser, but you will still get a definitive result.

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About JSON Validator

Most JSON bugs are not logic bugs, they are punctuation bugs. A trailing comma after the last key in an object, a pair of single quotes pasted out of a Python dict, an unescaped newline inside a string, or a smart quote that autocorrect snuck in. Each one produces a wall of text in the console and a request that fails before it reaches your handler.

The JSON Validator checks a document against the strict JSON grammar and reports exactly what went wrong, including the line and column where the parser gave up. That position is the whole point. Instead of scanning a thousand-line response by eye, you jump straight to the offending character.

It also runs the checks you would otherwise forget, such as rejecting comments, NaN, and Infinity, which are legal in JavaScript object literals but not in JSON. If your payload is genuinely valid you get a clean confirmation, which is genuinely useful before you wire a new endpoint into production.

When to Use This Tool

  • Checking a request body before sending it to an API that returns opaque errors
  • Verifying webhook payloads you are about to persist or process
  • Confirming that a config or secrets file is valid JSON and not JSON5
  • Debugging a deserialization failure in PHP, Node, or a database import
  • Reviewing a third-party SDK response that may contain NaN or comments