Fingerprint card · rolled impressions · black ink
Hash Generator
Type or drop in a file. Six impressions roll onto the card, one per algorithm, each unique to exactly this input. Paste a hash you were given into the verify line and the card tells you whether it matches.
Six impressions of one input
A hash is a fingerprint for data: a fixed-length string computed from the bytes so that the same input always gives the same hash and any change, one character, one bit, gives a completely different one. You cannot get the input back from it. That makes hashes the way to check that a download arrived intact, that two files are identical, or that a password was typed correctly without storing the password itself.
Which algorithm
SHA-256 is the everyday choice: fast, 64 hex characters, and what most checksums, certificates and blockchains use. SHA-512 and SHA-384 are its bigger siblings. MD5 and SHA-1 are still printed on old download pages, so the card rolls them too, but neither should protect anything new: collisions can be manufactured for both. CRC-32 is not cryptographic at all, just a quick eight-character error check used inside ZIP and PNG files.
Why a fingerprint card
The FD-258 card takes ten rolled impressions and four plain ones, each in its own box, and identifies a person from them alone. This card takes six impressions of your input. The ridge pattern in each box is drawn from the hash bytes, so two inputs never roll the same print.
Where do the hashes run?
In your browser. SHA-1, SHA-256, SHA-384 and SHA-512 use the browser's built-in Web Crypto; MD5 and CRC-32 are small routines on the page because Web Crypto does not provide them. Nothing is sent anywhere.
How do I check a downloaded file?
Print the file, then paste the checksum from the download page into the verify line. The card names the algorithm it matches; a mismatch means the file is corrupt or not the one you were promised.
Is Base64 the same hash?
Yes, the same bytes written differently: 44 characters for SHA-256 instead of 64. Some tools, Subresource Integrity for one, want the Base64 form.