Get a snapshot
An assumeUTXO snapshot, fetched in this tab over WebTorrent from whoever is seeding it, hashed as the bytes arrive, and compared with the sha256 the record states. Nothing is saved to disk unless you click Save. Any snapshot with a torrent on the record can be loaded by ?snapshot=network-height, or any snapshot page anywhere by its URI. A playground beside the assumeUTXO record.
The file
Fetch and check
Your browser joins the swarm over WebRTC and reads the web seed too. The whole file is held in memory while it is checked, so this is for files that fit in RAM.
not started
sha256 not computed
How it checks
The page reads the torrent from its own JSON-LD island, streams the file in order through a SHA-256 in plain JavaScript, and compares the digest with the island's sha256. Pieces are also checked against the infohash by WebTorrent as they arrive, so a peer cannot hand you wrong bytes; the sha256 is the link back to the record, which carries the same number. Source: play-grounds/webtorrent.