Generate Checksum computes a fixed-length fingerprint of any text using MD5, SHA-1, SHA-256, or SHA-512. Feed it the same input twice and you get the same hash every time; change even a single character and the entire output changes unpredictably — a property called the avalanche effect. That behavior is what makes hashes useful for integrity checking: instead of comparing two potentially large files or blocks of text byte by byte, you compare two short hex strings.
A checksum and a cryptographic hash are related but not identical concepts. Historically, "checksum" referred to simple error-detection schemes like CRC32, designed to catch accidental bit flips from noisy transmission lines, not to resist deliberate tampering. MD5, SHA-1, and the SHA-2 family (SHA-256, SHA-512) are cryptographic hash functions — built to make it computationally infeasible to find two different inputs that produce the same output (a "collision") or to reverse-engineer the input from the output. In practice, people use "checksum" loosely to mean any of these hashes when the goal is verifying that a file or string was not corrupted or altered, whether or not real adversarial security is at stake.
MD5 and SHA-1 are both cryptographically broken in the collision-resistance sense — researchers have demonstrated practical collision attacks against both, meaning it is feasible to construct two different files that hash to the same MD5 or SHA-1 value. That does not make them useless: MD5 is still widely used for accidental-corruption checks (like confirming a download was not truncated), and countless legacy systems still expect an MD5 or SHA-1 checksum for compatibility. It does mean neither should ever be trusted where an attacker could deliberately engineer a collision — digital signatures, certificate fingerprints, or anything security-critical belongs on SHA-256 or SHA-512, which have no known practical collision attacks as of today.
One thing a checksum tool is never appropriate for is password storage. Hashing a password with SHA-256 and storing the result is a common beginner mistake — general-purpose cryptographic hashes are deliberately fast, which is exactly wrong for passwords, because it lets an attacker with a stolen hash database try billions of guesses per second. Password storage needs a slow, memory-hard algorithm designed for that purpose specifically — bcrypt, scrypt, or Argon2 — never a raw hash function.
Need to see multiple algorithms side by side at once? Generate Cryptographic Hash computes SHA-1/256/384/512 simultaneously.
