JWT Verifier
Verify JWT signatures with secret key validation
JWT token input
Paste a token and optionally provide a secret. For example, verify an HS256 token from Authorization: Bearer. This can fail if the alg doesn’t match your secret type (HS vs RS).
JWT Token
Secret Key (Optional)
Leave empty to decode without signature verification
Verification result
See validity plus decoded header and payload when available.
Enter a JWT token above to verify its signature and claims
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Try Now JWT CreatorWhat is JWT Verifier?
A JWT Verifier is a critical security tool that validates the authenticity and integrity of JSON Web Tokens through cryptographic signature verification. Unlike simple JWT decoders that only read token contents, our JWT Verifier performs comprehensive validation by checking the digital signature against a provided secret key or public key. This process ensures that tokens haven't been tampered with, were created by a trusted source, and are still valid. The tool supports multiple signing algorithms including HMAC (HS256/384/512), RSA (RS256/384/512), and ECDSA (ES256/384/512), making it compatible with various JWT implementations. It validates not only signatures but also token structure, expiration times, and claim integrity. This verification process is essential for secure authentication systems, as it prevents token forgery, unauthorized access, and man-in-the-middle attacks. The tool is invaluable for developers implementing JWT-based authentication, security engineers auditing token systems, and anyone working with secure API authentication.
When to Use JWT Verifier
Use our JWT Verifier whenever you need to validate the authenticity and security of JWT tokens in your applications or systems. This tool is essential when implementing JWT authentication, debugging security issues, or testing token validation logic. Security engineers use it during penetration testing and security audits to verify that JWT implementations are secure and properly configured. Developers commonly use it when integrating with third-party authentication services, troubleshooting login failures, or ensuring that their JWT creation and verification processes are working correctly. It's particularly valuable when migrating between different JWT libraries, updating signing algorithms, or investigating suspected token tampering. The tool is also crucial for compliance audits, security reviews, and when you need to verify that tokens from external sources are legitimate and haven't been compromised.
How to Use JWT Verifier
7 stepsPaste the complete JWT token you want to verify into the token input field
Enter the secret key or public key used to sign the token
Select the correct signing algorithm (HS256, RS256, etc.) from the dropdown
Click the verify button to perform signature validation
Review the verification result showing success or failure with detailed error messages
Check the decoded payload and header information for additional validation
Examine expiration times and other claims to ensure token validity
Privacy & Security
100% SecureYour JWT tokens and secret keys are processed entirely within your web browser using client-side JavaScript cryptography. No tokens, secrets, or keys are transmitted to our servers or stored anywhere outside your device. This ensures complete security and privacy for sensitive authentication data, production secrets, and confidential JWT verification. The tool works offline once loaded, providing an additional layer of security for critical security validation tasks.
Pro Tips
7 tipsAlways use the exact secret key that was used to sign the token - even small differences will cause verification to fail
Verify that the algorithm specified in the JWT header matches the algorithm you select in the verifier
Check token expiration times carefully, as expired tokens should be rejected even with valid signatures
Use strong, unique secret keys for HMAC algorithms (HS256/384/512) to prevent brute force attacks
For RSA and ECDSA algorithms, ensure you're using the correct public key that corresponds to the private key used for signing
Test JWT verification in your application code using the same parameters you validate here
Never share secret keys in production environments - use environment variables or secure key management systems
Frequently Asked Questions
5 Q&AQ1:What is JWT signature verification and why is it important?
JWT signature verification confirms that a token hasn't been tampered with and was created by a trusted source. The signature is created using a secret key or private key, and verification ensures the token's integrity and authenticity. This is crucial for security as it prevents token forgery and unauthorized access.
Q2:What's the difference between JWT decoding and verification?
JWT decoding simply reads and displays the token's contents without checking authenticity. Verification goes further by validating the signature using the secret key, checking expiration times, and ensuring the token is legitimate. Always verify JWTs in production applications, not just decode them.
Q3:Which signing algorithms does this verifier support?
Our JWT verifier supports common algorithms including HS256, HS384, HS512 (HMAC with SHA), RS256, RS384, RS512 (RSA with SHA), and ES256, ES384, ES512 (ECDSA with SHA). The algorithm is specified in the JWT header and determines how the signature should be verified.
Q4:Is it safe to use this tool with production JWT secrets?
While our tool processes everything client-side for security, we recommend using test tokens or development secrets only. For production verification, implement JWT verification directly in your application code using trusted libraries rather than online tools.
Q5:What should I do if JWT verification fails?
Verification failure usually indicates wrong secret key, algorithm mismatch, expired token, or token tampering. Check that you're using the correct secret key, verify the algorithm matches your JWT creator, and ensure the token hasn't expired or been modified.
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