Zero Egress Costs: How I Built P2P File Sharing with Cloudflare

TL;DR I built a P2P file sharing tool where files transfer directly between browsers. The server only handles WebRTC signaling — actual files never touch it. Transfer a 10GB file? Still zero egress costs. The stack: Hono + Cloudflare Workers + Durable Objects + STUN. Demo: https://share-files.karakuri-maker.com/ Repo: https://github.com/kiyo-e/p2p-share-files The Problem: Egress Costs Add Up Fast Every file sharing service charges you for bandwidth. S3, R2, whatever — you pay for every byte that leaves the server. I ran the numbers for a simple use case: sharing large video files with a few friends. Even with Cloudflare R2's "generous" free tier, a few 4GB files per month and I'm paying. Scale that to actual users? The bill gets ugly. I wanted something different: zero transfer costs, regardless of file size. The answer was obvious in hindsight — don't let files touch the server at all. The Solution: WebRTC + Cloudflare WebRTC lets browsers