JWT Structure Validator
Paste a JWT token to check whether it is valid — complete with the reason if it is invalid and a component breakdown if it is valid. Everything is processed on your device.
Everything runs in your browser. Your data is never sent to our servers.
Example
Example Input
eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxMjM0In0.abc
Example Output
✓ VALID — alg HS256, sub 1234
How to Use
- 1Paste the a JWT token you want to check into the input box.
- 2If the tool offers extra options (e.g. dialect, flags, or variant), set them as needed.
- 3Click Validate (or press Ctrl+Enter).
- 4Read the result badge — VALID, INVALID, or VALID with a warning — along with the details and the list of issues, if any.
About JWT Structure Validator
JWT Validator checks the structure of a JSON Web Token: three dot-separated base64url parts, a header and payload that are valid JSON, then it checks the time claims (exp/nbf) and flags the dangerous "none" algorithm. An expired token is flagged as a warning.
Important: this tool validates STRUCTURE & CLAIMS, not the SIGNATURE. To verify the signature with a key/secret, use JWT Verify in the Cryptography category.
FAQ
Is my data sent to a server?
No. All validation runs in your browser with JavaScript. Nothing is uploaded, logged, or stored on our servers — safe for sensitive data.
How is this validator different from a parser or formatter?
A validator answers one question: is this input correct/valid? It returns a valid/invalid badge with the reason. A parser breaks input into its components, and a formatter tidies its layout. Use a validator when you just need to confirm something is sound before using it.