hash-hmac.underscoredone.com

Give this API any text or binary data and it instantly returns its fingerprint under whichever hash algorithms you choose — SHA-256, SHA-512, MD5, BLAKE2, CRC32, and more. It also signs data with a secret key (HMAC) and, most importantly, safely verifies whether an incoming signature matches — using a timing-safe comparison that prevents secret-leaking attacks. Language models cannot perform hashing: they produce a string of the right length and character set that looks correct but is simply wrong. Every webhook verification, idempotency key, cache fingerprint, or integrity check that relies on a hallucinated hash is silently broken. This API is the cure.