JWT Signature Validator
Check whether a JSON Web Token signature matches the supplied verification material. The validator helps diagnose malformed, modified, expired, or incorrectly signed tokens while keeping the operation in your browser.
Local Processing
Your tool input is processed locally in your browser and is not sent to DevToolsLabs servers.
How to use this tool
- Paste the complete JWT into the token field.
- Select the algorithm and provide the required verification key or secret.
- Run validation and review the signature result and decoded claims.
- Never paste production credentials into a device you do not trust.
When to use this tool
- Debugging authentication failures between services.
- Checking whether a token was changed after it was issued.
- Verifying test tokens while developing an API integration.
Frequently Asked Questions
Is decoding the same as validation?
No. Anyone can decode a JWT payload. Validation checks its cryptographic signature using the appropriate secret or public key.
Are tokens sent to DevToolsLabs?
No. Token inspection and supported signature checks run in your browser.
Built by Developers, For Developers
DevToolsLabs is maintained as an open-source collection of focused developer utilities. Most transformations run locally in your browser; tools that require a network service disclose the destination beside the tool. Each utility is built around a concrete development workflow and can be reviewed in the public source repository.