Kerim Sabic

Posted on May 17

Building an open-source Windows file transfer app with Rust, Tauri and QUIC

#rust #tauri #opensource #networking

Building an open-source Windows file transfer app with Rust, Tauri and QUIC

I recently launched Lightning P2P, an open-source Windows file transfer app.

The idea is simple:

Select a file → generate a link or QR code → receive the file.

No account.

No cloud upload.

No artificial storage dashboard.

Just direct-first file transfer.

GitHub: https://github.com/Kerim-Sabic/lightning-p2p

Product Hunt: https://www.producthunt.com/products/download-lightning-p2p

Why I built it

File transfer still feels more complicated than it should, especially on Windows.

If you want to send a file from one device to another, you usually end up with one of these options:

upload it to cloud storage
send it through a messaging app
use a USB cable
use a tool that only works on the same LAN
create an account somewhere
deal with file-size limits
use something powerful but too technical for normal users

AirDrop solved this feeling well inside Apple’s ecosystem.

But outside that ecosystem, especially for Windows users, the experience still feels fragmented.

I wanted to build something closer to:

“I have a file. I want to send it now. I do not want to create an account or upload it somewhere first.”

That became Lightning P2P.

What Lightning P2P does today

The current release is Windows-first.

It lets you share files using a simple receive link or QR code flow.

Current state:

Windows release available
Android sideload alpha
open-source
no account system
no cloud storage bucket
direct-first transfer
relay fallback when direct connection is blocked
sender must stay online during transfer

The goal is not to make another complicated sync tool.

The goal is a simple file transfer experience that normal users can understand, while still being technically serious underneath.

Tech stack

The current stack is:

Rust for the backend
Tauri for the desktop app
iroh/QUIC for the transfer layer
BLAKE3 for file verification
mDNS for nearby discovery
Windows-first packaging
Android alpha for receiving/testing flows

I chose Rust because this type of app needs reliability, performance, and a strong foundation for networking and file handling.

I chose Tauri because I wanted a desktop app that feels lightweight and native enough, without shipping a massive Electron-style bundle.

For the transfer layer, iroh/QUIC is interesting because it supports a modern direct-first networking model while still allowing relay fallback when direct connections are blocked.

Direct-first does not mean “direct always”

One important design decision was to be honest about networking.

In an ideal world, two devices connect directly and transfer the file peer-to-peer.

In the real world, NATs, firewalls, corporate networks, mobile networks, routers, and operating systems make this harder.

So the model is:

Try direct transfer first.
Use relay fallback when direct connection is blocked.
Avoid using a cloud storage bucket as the primary transfer path.
Keep the sender online while the transfer is available.

This distinction matters.

Lightning P2P is not trying to pretend that networking is magic. The product should explain clearly what happens, what is private, and what limitations exist.

Security and trust model

The current security model is still being improved, but the basic principles are:

no account required
no cloud storage bucket
transfer links / QR codes act like capability tokens
anyone with a valid receive link can request the file while it is available
BLAKE3 is used for verification
the sender must remain online
nearby discovery should be treated as suitable for trusted networks

This is one of the areas where I especially want feedback.

File transfer apps are easy to make look simple, but the trust model needs to be precise.

Users should understand:

who can access the file
whether the file is uploaded somewhere
whether a relay can store the file
whether the sender must stay online
what happens if a link is shared accidentally
what happens on public Wi-Fi
what guarantees the app does and does not provide

I would rather be conservative and clear than make vague claims.

What makes this different from existing tools?

There are already good tools in this space.

Some examples:

AirDrop
LocalSend
Magic Wormhole
Syncthing
Snapdrop / PairDrop
WeTransfer
Dropbox
Google Drive

I am not trying to claim that Lightning P2P replaces all of them.

The difference is the product direction.

AirDrop has the best mainstream UX, but it is locked inside Apple’s ecosystem.

LocalSend is excellent, especially for LAN transfer.

Magic Wormhole is technically elegant, but it is more comfortable for technical users.

Syncthing is powerful, but it is more of a sync system than a quick “send this file now” flow.

Cloud tools are familiar, but they usually involve accounts, uploads, storage limits, and a different privacy model.

Lightning P2P is trying to sit in a specific place:

simple enough for normal Windows users, open enough for developers, and direct-first enough for people who do not want every file transfer to become a cloud upload.

What I am not claiming yet

I am not claiming speed leadership.

Proper public benchmarks still need to be published.

I also do not want to oversell the current state. This is still early.

Current limitations:

Windows is the main supported platform
Android is alpha/sideload only
macOS and Linux are planned but not shipped yet
sender must stay online
public benchmarks are not ready yet
receive links need to be treated carefully because they act like capability tokens

I think open-source projects earn trust faster when they are clear about what is missing.

What I want feedback on

I would really appreciate feedback from developers, open-source builders, Windows users, and anyone who has worked on networking or desktop apps.

The main areas where feedback would help:

NAT traversal reliability
relay fallback model
security model
receive-link capability tokens
installer trust and signing on Windows
Android UX
whether macOS/Linux should come next
README clarity
benchmarks to include
comparison with existing tools

GitHub issues, comments, criticism, and suggestions are all useful.

Roadmap

The near-term roadmap is:

Improve the Windows release experience
Add a clearer demo GIF/video
Publish public benchmarks
Improve security documentation
Improve Android alpha
Add macOS/Linux support
Add clearer comparison docs
Improve NAT traversal diagnostics
Add more contributor-friendly issues
Build a stronger open-source community around the project

Longer term, I would like Lightning P2P to become a trusted open-source file transfer layer that works across platforms without forcing users into accounts or cloud storage.