For centralized signaling but p2p transfer: * webrtc * socket.io or datachannels For truly decentralized: * webtorrent * secure-scuttlebutt And of course,

For centralized signaling but p2p transfer: * webrtc * socket.io or datachannels For truly decentralized: * webtorrent * secure-scuttlebutt And of course, Ethereum and Bitcoin exist, but they're hard to take advantage of in a browser with decentralized trust. What kind of apps are you thinking of?