Hash Generator

What a hash function produces

A cryptographic hash maps any input, from a word to a gigabyte file, to a fixed-length fingerprint. The same input always yields the same digest, a tiny change flips roughly half the output bits, and you cannot work backward from a digest to the original. MD5 produces 128 bits, SHA-1 produces 160, and SHA-256 produces 256 bits, usually shown as hexadecimal.

Example

SHA-256("hello")
= 2cf24dba5fb0a30e26e83b2ac5b9e29e
  1b161e5c1fa7425e73043362938b9824

Change a single letter and the entire digest is unrecognizable, which is exactly what makes hashes useful for detecting whether a file or message was altered.

Pick the right algorithm

MD5 and SHA-1 are broken for security purposes: researchers can craft two different inputs with the same digest (a collision). That makes them unsafe for signatures or certificates. They are still fine as fast non-security checksums, for example a cache key or a quick integrity check against accidental corruption. For anything security-related use SHA-256 or stronger.

Hashing is not for passwords directly

A raw SHA-256 of a password is still weak, because attackers can test billions of guesses per second. Password storage needs a deliberately slow, salted algorithm such as bcrypt, scrypt, or Argon2. A plain hash tool is the wrong instrument for that job.

FAQ

Can I get the original text back from a hash? No. Hashing is one-way. Any site that claims to reverse a hash is really just looking the input up in a precomputed table of common values.

Why do two files give the same MD5? That is a collision, and it is why MD5 should not be trusted where an attacker controls the input.

Does uppercase vs lowercase hex matter? No, they represent the same bytes. Just stay consistent when comparing digests as strings.