PlainICU Frequently Asked Questions
What is PlainICU?
PlainICU (plain.icu) is a minimal browser-based file/text transfer tool. No app install needed — open this site in a browser and devices on the same network discover each other, then transfer files directly peer-to-peer over WebRTC. The server only helps them find each other; it never touches your data.
How do I send a file to another device?
Open this page on both devices (ideally on the same network). Once the second device appears in the list, drag and drop or select your files — they transfer directly to the other device.
Do my files ever touch a server?
No. Transfer is fully peer-to-peer over WebRTC. The signaling server only helps devices discover each other and exchange connection details; it never sees the file bytes, so your data never leaves your devices.
Do I need an Internet connection?
On the same network: no — devices connect directly over the LAN.
Is there a file size limit?
No preset limit. Because files stream directly between devices, the only real constraints are your devices' memory, storage, and connection speed.
Is the transfer encrypted?
Yes. WebRTC encrypts each data channel with DTLS, so the bytes are secured end-to-end between the two devices before anything is sent.
I can't find the other device while a VPN is on. What should I do?
A VPN routes your traffic through an encrypted tunnel, which can hide your device inside a virtual network and prevent LAN discovery. Try turning off the VPN when transferring over the same network, or make sure both devices are connected to the same virtual network.
Why can't I see the other device with a dual WAN (load-balanced) router?
A dual WAN router can spread the two devices' traffic across different internet connections, mapping them to different public IPs. Since PlainICU only lists devices that share the same public IP, the two devices can't see each other or connect. Fix: pin both devices to the same WAN line in your router (e.g., port/device binding, policy-based routing, or simply disabling load balancing), or put both devices on the same network before transferring.