File hash
Get a file's fingerprint
Drop in any file and this computes its cryptographic hash, a short fixed string that acts as the file's exact fingerprint. Change a single byte and the hash changes completely, so it is the standard way to check that two files are identical or that one has not been altered.
Runs entirely in your browser. Your file is never uploaded or stored.
Hashing…
What a hash is for
A hash function turns a file of any size into a fixed-length string. The same file always produces the same hash, and any change, even one bit, produces a completely different one. That makes a hash useful for three everyday jobs: confirming a download arrived intact, checking that two files are byte-for-byte identical without comparing them directly, and recording a file's state at a point in time so you can prove later that it has not changed.
Which one to use
SHA-256 is the sensible default and what most tools and evidence logs expect. SHA-512 is the same idea with a longer digest. SHA-1 is shown because a lot of older systems and malware databases still index by it, but it is cryptographically broken for security purposes and should not be relied on to prove a file was not tampered with. This tool computes all three so you can match whichever a given system uses.
What a hash does not tell you
A hash proves sameness, not authenticity. Two files with the same hash are identical, but a hash on its own says nothing about where a file came from or whether its contents are genuine. It only becomes evidence of integrity when the original hash was recorded by a trusted party at a trusted time. Browse the full tool set for the checks that read what is inside a file.