Hash Generator

What a hash is

A hash turns any input into a fixed-length fingerprint. The same input always produces the same hash, and any change — a single character, a single bit — produces a completely different one. You cannot work backwards from the hash to the input.

That makes hashes useful for checking that something has not changed: compare the hash of a file you downloaded against the one the publisher listed, and if they match, the bytes match.

Which algorithm to use

• SHA-256 — the sensible default for anything new.
• SHA-512 — longer output, same family, no practical downside.
• SHA-1 — broken for security since 2017. Fine for a non-security checksum, not for anything that matters.
• MD5 — thoroughly broken. Still widely used for file checksums where the only concern is accidental corruption, never for security.

Hashing is not encryption

Encryption is reversible with a key; hashing is not reversible at all. If you need to get the original back, you want encryption, not this.

And hashing a password by itself is not password storage. Real password storage uses a slow, salted algorithm such as bcrypt or Argon2, specifically so that guessing is expensive. A plain SHA-256 of a password can be brute-forced at enormous speed.

Frequently Asked Questions

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