Files are sent directly between the two browsers using WebRTC,
over a connection that's end-to-end encrypted (DTLS) the same
way a video call would be. The server only helps the two
browsers find each other at the start (signaling) — it never
receives, stores, or has access to the file itself.
Establishing that direct connection depends on both people's
network setups (NAT/firewall behavior). It usually works, but
isn't guaranteed on every network — see the project's
CONNECTIVITY-EXPLAINED.md for the technical
details if a connection fails to establish.
Recommended browser: Google Chrome (or another
Chromium-based browser) gets the best experience for large
files — it can stream a received file straight to disk.
Firefox and Safari currently buffer the whole file in memory
before it downloads, which is more limited for very large
transfers.