Crypto Tools
MD5 Hash
Hash a string with MD5, with optional HMAC key authentication. Computed locally, nothing is uploaded.
HMAC is a message authentication code built on a hash function and a secret key. It verifies that data is intact and really comes from who it claims to. Published as RFC 2104 in 1997, it is used widely in IPSec, TLS/SSL and similar protocols.
About MD5
MD5 (Message-Digest Algorithm 5) is a widely used cryptographic hash function, designed by Ronald Rivest in 1991. It turns data of any length into a 128-bit (16-byte) digest, usually written as 32 hexadecimal characters.
MD5 is a message-digest algorithm, not an encryption algorithm — it is one-way: you can compute the digest from the input, but you cannot get the input back from the digest. It is still used for file integrity checks and as a helper in signature verification. Practical collision attacks exist, so do not use MD5 on its own to store passwords; reach for a password hashing algorithm such as bcrypt or Argon2 instead.
About HMAC
HMAC (Hash-based Message Authentication Code) adds a shared secret key on top of the hash function, so only parties holding the key can compute and verify the code. That is what keeps a message from being altered or forged along the way.
16-character vs 32-character
Standard MD5 output is a 32-character hex string (128 bit). The 16-character version keeps only characters 8–24, which halves the information and pushes the collision probability sharply up — do not use it where security matters. It only makes sense for lightweight jobs where uniqueness does not matter much, such as generating short IDs.