What's the hash of this?
Type text or drop a file to get its SHA-256. Paste the hash you were expecting and it will say whether they match, which is the reason you usually want one. Files are read in pieces, so size costs time and not memory.
Questions people actually ask
- Is my file uploaded?
- No. Your browser does the hashing itself, using the same cryptography built into it for HTTPS. The file is read from your disk and never leaves the machine.
- How big a file can I hash?
- As big as you have patience for. The file is read in pieces rather than all at once, so size costs time and not memory.
- Where are MD5 and SHA-1?
- Left out. Both can be forced to produce the same hash for two different files, which defeats the point of checking one. If a download page still lists an MD5, treat it as a typo check and not a security one.
- Why only SHA-256?
- Because it is the one that can be computed without loading the whole file into memory. The browser's built-in hashing has no way to be fed a file a piece at a time, so this page brings its own SHA-256 — and writing a second one for the 384 and 512 variants would buy almost nobody anything. SHA-256 is what download pages publish.
- Why doesn't my hash match the website's?
- Check for stray spaces first — hashing "abc" and "abc " gives completely different answers, which is what makes hashes useful. Then check you picked the same algorithm. If both are right, the file really is different.