Verify HS256 JWT Signature Online

HS256 (HMAC-SHA256) is the most common JWT signing algorithm. It uses a shared secret known to both the token issuer and the verifying party. To verify an HS256 token you need the exact same secret string used to sign it.

This tool uses the browser's built-in SubtleCrypto API to import your secret as an HMAC-SHA256 key and run the cryptographic verification — no JavaScript library required, no network call made. Your token and secret never leave your device.

Common use cases: debugging auth middleware, confirming a staging secret matches production, verifying a third-party service's tokens before trusting them in your backend.