JSON Validator
Instantly validate JSON code and find exactly where the error is
About JSON Validator
Fastols' JSON Validator checks any JSON code and instantly tells you whether it's valid or has a syntax error, pinpointing the type and approximate location of the problem so you can fix it fast instead of scanning line by line.
It's useful before you use an API response or a config file in your project, to make sure it matches the official JSON format. Validation happens entirely inside your browser — nothing is uploaded to any server.
How to use JSON Validator
- 1Paste your JSON code into the box
- 2See the validation result instantly: Valid ✓ or the error details
- 3Fix the error and paste again to confirm the code is now valid
Frequently Asked Questions
How is JSON Validator different from JSON Formatter?
JSON Validator focuses on checking correctness and gives you error details, while JSON Formatter also returns a nicely indented, formatted version of the code.
Is the tool completely free?
Yes, it is 100% free with no usage limit and no account required.
Is my JSON data stored anywhere?
No, validation happens entirely inside your browser — no data is uploaded or stored on any server.