JWT Signature Validator
Verify JWT token signatures with a secret key
Input
Enter JWT and secret key
Result
Validation result
Enter a JWT and secret key, then click validate...
About JWT Signature Validation
JWT signature validation verifies that a token was created with a known secret key and hasn't been tampered with. This tool supports HS256 (HMAC-SHA256) signatures.
Verify the cryptographic signature of JSON Web Tokens using HMAC SHA-256. Paste a JWT and your secret key to determine if the signature is valid. All verification is performed in your browser using the Web Crypto API.
Key Features
- ✓HS256 signature verification
- ✓Web Crypto API — browser-only
- ✓Header and payload decoding
- ✓Valid/invalid visual indicator
- ✓No data sent to server
How to JWT Signature Validator
- 1
Paste JWT
Enter a complete JWT (header.payload.signature).
- 2
Enter secret
Provide the signing secret key.
- 3
Verify
Click verify to check if the signature is valid.
Common Use Cases
- •Debugging JWT authentication issues
- •Verifying token signatures in development
- •Checking if a JWT was tampered with
- •Testing API authentication flows
Frequently Asked Questions
What algorithms are supported?▼
Currently HS256 (HMAC SHA-256). RS256 and other asymmetric algorithms require public key verification.