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Hash generator

All three at once, because the page that published the checksum you are checking rarely says which algorithm it used.

Files are read in slices in this page rather than uploaded, and the progress is real.

What to hash

Hashed as UTF-8, so text in any language gives the same answer any other correct tool would.

SHA-256waiting for something to hash
SHA-1waiting for something to hash
MD5waiting for something to hash

Questions

Is what I paste sent anywhere?
No. Every tool in this kit runs in the page itself. There is no server here that receives what you paste, and you can check it in your browser's network tab: using a tool produces no request carrying your input at all.
Which of the three should I use?
SHA-256 for anything that matters. SHA-1 and MD5 are both broken for security: two different files can be made to share a digest deliberately. They are here because a great many checksums and older APIs still quote them, and checking a download against a published MD5 is a reasonable thing to want to do.
How is text hashed?
As its UTF-8 bytes, which is what every other correct tool does. That means text in any language gives the answer you can check against any other implementation.
How large a file can it handle?
The MD5 streams properly, a slice at a time, so size is not the limit there. The browser's built-in digest has no streaming interface, so for SHA the slices are joined before hashing, which does cost memory on a very large file. That is a real limit and it is better said than hidden.

The other tools here