I want to share a tool that solves a problem every developer runs into constantly: getting a file from one device to another as fast as possible, without friction.
The problem
You're on your phone and need to get a screenshot to your laptop. Or you need to send a file to someone in the same room. The usual options: AirDrop (Apple only), email it to yourself, upload to Google Drive, or fumble with a USB cable. All slower than they should be.
What 5g.chat does
https://5g.chat — open it in any browser, pick your files, get a 6-digit code. Open it on the other device, enter the code. Files transfer directly, device to device. Done.
No account. No app. No file size limit. Works on Chrome, Safari, Firefox, Edge.
How it works under the hood
It uses WebRTC data channels — the same technology that powers browser-based video calls, but used here to stream raw file bytes directly between two browsers.
The architecture:
- A lightweight WebSocket signaling server brokers the initial connection (SDP offer/answer + ICE candidate exchange), then steps aside entirely
- Once the RTCPeerConnection is established, the server sees nothing — files go device-to-device
- Files are chunked at 16 KB with a 256 KB bufferedAmount ceiling for backpressure management
- STUN only (Google and Cloudflare public servers) — pure P2P, no TURN relay
- Sessions and codes expire after 30 minutes
- Client-side QR code generation for easy mobile pairing
Why this matters for privacy
The server's only involvement is helping two browsers find each other across NAT. It never touches the file payload. Nothing to store, nothing to log, no account to breach.
WebRTC data channels are encrypted via DTLS — transport-layer encryption, so the connection itself is secure.
The use case
Getting a file from point A to point B in under 30 seconds, with nothing to install on either end. That's it.
Try it: https://5g.chat
Curious to hear feedback — especially from anyone who's hit NAT traversal issues with pure STUN setups.
