Text to hash
Secret key
Verify against an expected hash (optional)
Hashing uses the browser's built-in Web Crypto (SubtleCrypto), so the algorithms are the real, standard ones. Text and key are encoded as UTF-8. HMAC follows the standard keyed-hash construction. The verify box compares your pasted hash against every algorithm (case- and spacing-insensitive) and flags a match. MD5 isn't offered because it's insecure and not provided by the browser. Everything runs on your device.