The verify page answers one question: did Yore issue this file? It works for two kinds of file, and needs no account.
How it works
Choose the file and press Check the file. Yore takes the file's SHA-256, looks it up among the exports and exhibits it issued, and deletes the file. It keeps nothing of it. A file may be 20 MB at most, and one address may check ten files a minute.
A match states that Yore issued a file with exactly these bytes, and when. For an export it adds how many pages and captures the manifest states. It never says whose plan it was or what the file holds.
No match says nothing about a file. It may be Yore's and changed since, by one byte, or it was never Yore's.
By hash
If you'd rather not upload the file, hash it yourself and ask by hash:
shasum -a 256 manifest.json
curl https://yore.steddle.com/api/v1/verify/<sha256>The answer is the same, as JSON. yore verify export.zip --online does both steps after its own check.
Without Yore
None of this is needed to trust an export's contents. Every file in an export is named by its hash, and each capture can be fetched again from the web archive. Check it by hand, or run yore verify offline.