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. In realtime mode, files stream directly from one device to
another over a WebRTC DataChannel and never touch any
server. An optional stored download-link mode encrypts files
in your browser (AES-256-GCM) before any upload, so the server holds
only zero-knowledge ciphertext. There is no installation, and no
server-imposed file-size limit in realtime mode. Realtime transfers
over the LAN or a pairing code need no account; creating a share link
or a stored download link requires the sender to sign in.
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 (realtime mode) — file bytes flow over WebRTC and never pass through the server, which only helps the devices find each other. An optional stored download-link mode keeps files as zero-knowledge ciphertext only you can decrypt.
- 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 install; realtime transfers need no account (share and download links require the sender to sign in).
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: in realtime mode, files go directly device-to-device, end-to-end encrypted, with no server copy and no server size cap; the optional stored download-link mode encrypts files zero-knowledge before any upload so the server never sees plaintext.
- 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 installation. Realtime transfers (LAN or pairing code) need no account; creating a share link or a stored download link requires the sender to sign in.
Do my files get uploaded to a server?
In realtime mode: no — files stream directly between the two devices over WebRTC and never touch the server. There is also an optional stored download-link mode where your browser encrypts files before upload and the server stores only zero-knowledge ciphertext (AES-256-GCM, key only in the URL fragment).
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.
Learn more
Also available in: 中文 · 日本語 · 한국어 · Deutsch · Français
Source code on GitHub.
A machine-readable summary for AI engines is at
/llms.txt.