Relayium — End-to-end encrypted peer-to-peer file transfer
Relayium is an open-source, end-to-end encrypted,
peer-to-peer (P2P) file transfer tool that runs entirely in your
browser. Files stream directly from one device to another over a
WebRTC DataChannel and never touch any server. There
is no account, no installation, and no server-imposed file-size limit.
How it works
- Open relayium.com on two devices on the same network — they discover each other automatically.
- Pick a file or drag and drop (up to 10 at once); the receiver accepts.
- Both screens show a 6-digit verification code — compare it to rule out a man-in-the-middle.
- The file streams device-to-device, end-to-end encrypted, and is verified with a per-file SHA-256 hash.
Why Relayium
- End-to-end encrypted — per-transfer X25519 key exchange and AES-256-GCM; keys never leave the two devices.
- Truly peer-to-peer — file bytes flow over WebRTC and never pass through the server, which only helps the devices find each other.
- Man-in-the-middle protection — a 6-digit Short Authentication String (SAS) on top of WebRTC's DTLS.
- Cross-platform — works between Windows, macOS, Linux, Android and iOS through any modern browser (Chrome, Edge, Firefox, Safari).
- Free and open source — MIT licensed, no account, no install.
How Relayium compares
- vs AirDrop: cross-platform and browser-based, not limited to Apple devices — works between, e.g., a Windows PC and an iPhone.
- vs WeTransfer or Google Drive: files are not uploaded to a server; they go directly device-to-device, end-to-end encrypted, with no server copy and no server size cap.
- vs Snapdrop / PairDrop: adds an application-layer end-to-end encryption layer (X25519 + AES-256-GCM) and a SAS verification code, so a malicious signaling server cannot read or MITM the transfer undetected.
Frequently asked questions
Is Relayium free?
Yes — free and open source under the MIT license, with no account or installation.
Do my files get uploaded to a server?
No. Files stream directly between the two devices over WebRTC and never touch the server.
Is it end-to-end encrypted?
Yes — X25519 key exchange and AES-256-GCM, with keys that never leave the two devices, plus a 6-digit code to detect man-in-the-middle attacks.
Can I send files between different operating systems?
Yes — it is browser-based, so Windows ↔ iPhone, Android ↔ Mac, and Linux ↔ anything all work.
What is the file-size limit?
No server-imposed limit. Chrome and Edge stream files to disk; in Firefox and Safari keep files under about 200 MB because they buffer in memory.
Source code on GitHub.
A machine-readable summary for AI engines is at
/llms.txt.