TL;DR: I built a P2P file transfer tool that runs entirely in the browser. No install, no server relay, no account. Here's what I learned about WebRTC data channels, resumable transfers, and the browser storage mess along the way. Most file transfer tools follow the same pattern: upload to a server, get a link, the recipient downloads from that server. Your file sits on someone else's infrastructure, at least for a while. I wanted to try a different approach: what if the file never leaves the browser at all? That question turned into TransP2P — a browser-based P2P file transfer tool built on WebRTC. In this post I'll walk through the technical decisions, the parts that were harder than expected, and the two browser storage paths that almost no one talks about. The basic architecture The flow is straightforward in theory: Both devices open the site (no install, no account). A WebSocket signaling server helps them exchange SDP offers/answers and ICE candidates. A direct WebRTC data channel is established.…