Checksum verify
Compare a file against an expected checksum, computed locally.
Runs on your device. The file is never uploaded.
Checksum verify hashes one file with hash-wasm and compares the digest against the hex string you paste, using sha256 unless you pick another algo. The result is four lines: the file name, the computed hash, the expected hash, and finally MATCH or MISMATCH by itself. A mismatch tells you the bytes differ, never where or how.
Questions
Which algorithms can I check against?
MD5, SHA-1, SHA-256, SHA-384, SHA-512 and CRC-32, chosen with the algo option, which defaults to sha256. The hash is computed with hash-wasm on your device. Pick the one matching the checksum you were given, since a SHA-256 hash will never match the MD5 of a file no matter how good the download was.
Does the case or spacing of my pasted checksum matter?
No. Both sides are trimmed of surrounding whitespace and lowercased before they are compared, so an uppercase hash from one site and a lowercase one from another both work. Hex is expected. Do not paste the file name that often follows a hash in a checksum file, only the hex digits.
What does the result look like?
Four lines: the file name, the algorithm with the hash it computed, the expected hash you supplied, and then MATCH or MISMATCH on its own line at the end. Seeing both hashes lined up makes it easy to spot a paste that lost a character.
What does a mismatch mean?
That the bytes you have are not the bytes the checksum was made from. Usually that is an incomplete or corrupted download, or a checksum copied from a different version of the file. It can also mean you picked the wrong algorithm. Re-download and check again before assuming anything worse.
Does it change my file or upload it?
Neither. The file is read and hashed in your browser and nothing is written or sent. That is the point of checking a checksum locally: sending a file somewhere to ask whether it is intact would defeat the purpose. No output file is written either, so the verdict text on the page is the whole result.
How large a file can it hash?
There is no fixed limit, but the whole file is held in memory while it is hashed, so a large download can exceed what a browser tab holds. There is no output file, only the verdict text, so memory goes on the input alone.