Computed by your own browser, which is the only sensible place to hash something you care about. Pasting a secret into a website that hashes it on its server rather defeats the point.
This page loads no libraries at all — the work is done by the browser itself.
Your file is read on your own machine and never sent anywhere — open your
browser's network tab and watch while you use it.
Questions
Where is MD5?
Deliberately absent. It is broken for anything security-related, and the browser crypto API does not offer it — which we take as a hint rather than a problem to work around.
Which one should I use?
SHA-256 unless something specific tells you otherwise. SHA-1 is here only for checking against old systems.
Other text & code tools
Everything here is free and works the same way — in your browser.