Developer ToolsCode ValidatorsFree Tool
JWT Validator
Decode a JWT and check its structure, algorithm, and expiry claim — without verifying the cryptographic signature.
How to Use JWT Validator
- 1Paste your JWT (header.payload.signature)
- 2Click Process
- 3Review the decoded header/payload and expiry status
Frequently Asked Questions
No — signature verification requires the secret key or public key used to sign the token, which this tool never has. It explicitly shows '⚠ Signature not verified (requires the secret key)' in the output. A tampered token would not be detected by this tool.
That the token has the correct 3-part structure (header.payload.signature), successfully decodes as base64/JSON, and — if an exp claim is present — whether that timestamp has passed.
They're closely related — both decode the header and payload — but this Validator additionally checks the 3-part structure and expiry, and clearly flags decode failures as invalid rather than just showing raw output.
No — decoding happens entirely in your browser; the token is never transmitted.
Related Tools
JSON Validator
Validate JSON syntax in your browser using the same parser JavaScript itself uses, with the exact error message if parsing fails.
XML Validator
Validate XML well-formedness using the browser's built-in XML parser, reporting the root element and child count on success.
HTML Validator
Validate HTML5 markup for errors, accessibility issues, and best-practice warnings — instantly in your browser.
CSS Validator
Run basic heuristic checks on CSS — mismatched braces, likely missing semicolons, and empty rule blocks — not a full W3C validation.