About File Tunnel

What is File Tunnel?

File Tunnel is a real-time file transfer service designed for sending large files quickly and without storing them on a remote server. A sender shares a short transfer code; receivers enter the code and the file streams between the two browsers through a server-side WebSocket relay. Once the transfer ends, no copy of the file remains on our infrastructure.

Why we built it

Existing "upload then download" services keep your files on someone else's disk — sometimes for weeks. We wanted a tool that treats a file transfer the way a phone call treats a conversation: in the moment, end-to-end, and gone when it's done.

Who runs File Tunnel

File Tunnel is built and operated by a small independent engineering team based in Seoul. We work day to day with the messy realities of moving large files — flaky networks, browser storage limits, NAT traversal, chunked streaming protocols, and the trade-offs between speed, reliability, and privacy. The product and the guides we publish come from that hands-on experience, not from a content mill.

How it works

1. The sender selects a file. The browser splits it into 4 MB chunks on the fly.
2. A transfer code (12 characters) is generated. The sender shares it with the intended recipient.
3. The receiver opens the link or enters the code. A WebSocket connection opens to the relay.
4. The sender streams chunks; the relay forwards each chunk to all connected receivers; the receiver writes them to disk via StreamSaver, never holding the full file in memory.
5. If the connection drops, both sides reconnect and resume from the last verified chunk.
6. When the session ends, only minimal metadata remains, and it is auto-deleted on expiration.

Highlights

• No server storage: files are relayed in real time, never written to disk.
• One sender, many receivers: broadcast a file to multiple recipients at once.
• Resume support: reconnect and continue from the last verified chunk.
• Open architecture: any browser, any platform.
• Encrypted in transit: TLS protects every byte over the wire.

Technology

• Backend: Rust + Axum + Tokio + SQLx + PostgreSQL
• Frontend: Next.js (App Router) + TypeScript + Tailwind CSS
• Transport: WebSocket with binary chunk framing
• Integrity: per-chunk hashing

Limits and pricing

The current beta lets anyone send files up to 10 GB without signing in. Signed-in users get a higher free limit, and a paid plan (via LemonSqueezy) raises the cap further with additional features once stable.

Roadmap

• Multi-file and folder transfer
• QR-code-based phone ↔ PC handoff
• Password-protected transfers
• Optional WebRTC peer-to-peer mode
• CLI client for developers

How we write our guides

Our guides are written to stand on their own — to be useful even to a reader who never opens File Tunnel. We hold them to three rules:

• Accuracy first. We explain how the underlying technology actually works — TLS, WebRTC, chunked transfer, browser file APIs — and we revise an article when we find we got something wrong.
• Honest about limits. Every guide says when an approach is the wrong choice, not only when it shines.
• No dark patterns. Reference articles carry no sales pitch. We would rather lose a click than mislead a reader.

Get in touch

Questions, feedback, or partnerships: ssin6505@gmail.com. We read every message and reply in English or Korean. Bugs or feature ideas are welcome.