[eldod]

WebTorrent actually implements the bittorrent protocol, and can be used as a nodejs bittorent client. It extends the bittorent protocol to do p2p sharing inside the browser (but you only can connect to other people using the webtorrent nodejs app or in-browser app, and not all the bittorent network)

FilePizza and Bitfly are much simpler implementations, doing 1-to-1 file transfers in the browser using the basic WebRTC Datachannel API.

Looks like FilePizza is now using WebTorrent too now, as it's mentionned in their FAQ:

"Where are my files sent? Your files never touch our server. Instead, they are sent directly from the uploader's browser to the downloader's browser using WebTorrent and WebRTC. This requires that the uploader leave their browser window open until the transfer is complete."

https://github.com/kern/filepizza