Why you can trust this page
The file never leaves your machine. Checksum sites that ask you to upload the file defeat the entire purpose — you would be sending the thing you are worried about to a stranger. Here the security policy at the top of this file makes your browser refuse every network connection, so the file cannot go anywhere even in principle.
The arithmetic is checked before you rely on it. On every load, this page runs its SHA‑256 and SHA‑1 against the official test vectors, and against your browser's own independent implementation on random data. The result is printed at the bottom of the file list. Two implementations agreeing is evidence; one asserting is a press release.
SHA-256 is the one that matters. SHA‑1 is shown because older download pages still list it, and it remains fine for spotting corruption — but collisions can be manufactured for it, so treat it as a legacy cross-check. MD5 is deliberately absent: it has been broken since 2004, and printing it would lend it credibility.
You are reading the whole program. This one file is the entire tool and its own source — open it in a text editor, or attach it to an AI and ask what it does. What you check is what runs, because there is only the one file.