What a hash is

A hash is a short fingerprint of some data. The same input always gives the same hash, and changing even one character gives a completely different one. Hashes are used to check that a download wasn’t damaged or tampered with, to spot duplicate files and to index data.

How to use it

Text: type or paste text and all five hashes update at once. Text is hashed as UTF-8, the same as most programming languages, so a hash made here matches one made with sha256sum on the same bytes. A trailing newline counts, which is the usual reason two tools disagree.

A file: choose a file (up to 200 MB) and read its checksum. Paste the checksum the publisher gave you into the check box and the page tells you whether it matches, and which algorithm it belongs to. The file is read on your device and never uploaded.

Which one should I use?

SHA-256 or SHA-512 for anything where security matters. MD5 and SHA-1 are broken for security (attackers can make two different files with the same hash), but they are still common for catching accidental corruption. Hashes are not encryption and can’t be reversed, and a plain hash is not a safe way to store passwords.