About SHA-1

SHA-1 produces a 160-bit digest. Practical collisions were demonstrated in 2017 and browsers and certificate authorities have retired it, but it still appears in git object ids and older protocols.

Digests here are computed with the browser's WebCrypto API (MD5 runs locally in JavaScript, since WebCrypto dropped it). A hash is one-way: the same input always produces the same 160-bit digest, but the digest can't be reversed back into the input. Text you enter never leaves the page.