Start a room, then open its link or type its code on the other device.
Type the code (or paste the link) shown on the other device.
Both devices open the same room. A small server passes the connection details (network addresses and encryption fingerprints) between the two browsers, and from then on they talk to each other directly over WebRTC. Files and text go straight from one browser to the other, encrypted in transit (DTLS). They never pass through our server and are never stored anywhere but on the two devices.
No fixed limit. Files are read and sent in small pieces, and received pieces are written to your browser's storage as they arrive, so large files don't have to fit in memory. The practical limit is the free disk space your browser lets the site use.
A copy of each file or text you send or receive is kept in this browser's storage (IndexedDB) so you can download it again. Nothing is kept anywhere else. Copies expire after 7 days by default; you can change that, delete single items, or clear everything. Choose "Don't keep" and received files are held in memory only until you leave the page.
Anyone with the code, so share it only with your other device. A room holds two devices; while both are connected nobody else can get in. Room codes are random and not logged.
Some networks (strict office or school firewalls, some mobile carriers) block direct connections between devices, and some home routers won't connect two devices on the same network this way. When a room has a relay (Cloudflare's TURN service) the transfer goes through it instead, and the page says "Relayed"; the relay passes the encrypted stream along and can't read or keep it. Without a relay the transfer can't start on such a network; try another one, such as a phone hotspot. Each browser also asks Cloudflare's STUN server for its public address. No analytics run on this site.