Altersend

File transfer without the cloud.

Files go directly between your devices — end-to-end encrypted, no accounts, no servers, no limits.

Website · Download · Discord

 

Contents

• About
• Features
• Download
• How it works
• For developers
  • Prerequisites
  • Setup
  • Run
  • Build
  • Project structure
  • Tech stack
  • Crash reporting
• Contributing
• Security
• License

About

AlterSend is a free, open-source app for sending files directly between your devices — no cloud, no uploads, no size limits. Files transfer peer-to-peer and are end-to-end encrypted; nothing is ever stored on a server.

Why use WeTransfer, Dropbox, or Google Drive when you can send files directly — instantly, privately, with no upload costs and no limits?

Features

• No accounts — no signup, no login, no email address required
• No servers — files transfer directly device-to-device, nothing stored in the cloud
• End-to-end encrypted — only your devices can read your files, always
• No file size limit — send a 100 MB photo or 500 GB video archive, same experience
• Cross-platform — macOS, Windows, Linux, iOS, Android
• Works everywhere — local network or across continents, same code path
• Open source — Apache-2.0, audit every line yourself

Download

Get the latest release from altersend.com/download or directly from the table below.

macOS .dmg — signed with our Developer ID but not yet notarized by Apple, so macOS will show "AlterSend cannot be opened because the developer cannot be verified" on first launch. Right-click the app → Open → Open to bypass Gatekeeper (one time only). Notarization is in progress.

Windows .exe — not yet signed, so Windows will show "Windows protected your PC" on first run. Click More info → Run anyway to install. The Microsoft Store version is signed and avoids this warning.

How it works

1. Open AlterSend on both devices
2. One device shows a join code (or QR)
3. The other scans or types it
4. Files transfer directly — peer to peer

   ┌─────────┐          encrypted P2P          ┌─────────┐
   │ Device  │ ◄──────────────────────────────► │ Device  │
   │   A     │     direct, no middleman         │   B     │
   └─────────┘                                  └─────────┘
        ▲                                            ▲
        │       peer discovery via Hyperswarm        │
        └────────────────────────────────────────────┘
                   (DHT, no central server)

Discovery uses Hyperswarm (a DHT) — once peers find each other, no central infrastructure is involved. Transfers run over Hyperdrive: encrypted, content-addressed, resumable.

For developers

Prerequisites

• Node.js 20+
• npm 10+
• Xcode (iOS) or Android Studio (Android)

Setup

git clone https://github.com/denislupookov/altersend.git
cd altersend
npm install

cp apps/desktop/.env.example apps/desktop/.env
cp apps/mobile/.env.example apps/mobile/.env
# All env vars are optional in dev — the app runs without them.

Run

npm run dev            # desktop (Electron)
npm run mobile:start   # mobile (Expo)

Build

npm run desktop:build  # packages + desktop app

Platform installers (.dmg, .exe, .AppImage) are produced by the release CI workflow — trigger manually from the Actions tab.

Project structure

apps/
  desktop/    Electron app — main + renderer + Bare worklet
  mobile/     React Native / Expo app
packages/
  core/       P2P protocol — Hyperswarm, Hyperdrive, RPC
  domain/     State management — Zustand store, business logic
  components/ Cross-platform UI — React Strict DOM + Tailwind
docs/
  architecture.md   Full system overview

See docs/architecture.md for data flow and inter-process boundaries.

Tech stack

Electron · React Native · Expo · Bare · Hyperswarm · Hyperdrive · React Strict DOM · Tailwind · Zustand

Crash reporting

Crash and error reporting uses Sentry. It is opt-in and off by default — nothing is sent until you enable it in the app's settings.

• Where it runs. Desktop has two Sentry SDKs: @sentry/electron/main for native main-process crashes and @sentry/electron/renderer for renderer JS / transfer errors. Mobile uses @sentry/react-native. The Bare worklet has no Sentry — it pipes its logs to the renderer over RPC instead.
• Opt-in state. Stored locally: desktop uses the localStorage key altersend.crash-reporting.enabled; mobile uses a marker file in the app document directory. The main process initializes Sentry early (before app ready) but gates submission in beforeSend; the renderer pushes the current preference over the sentry:setEnabled IPC channel.
• PII scrubbing. beforeSend rewrites home-directory paths to ~ in exception messages and breadcrumbs, so usernames and file paths don't leak into stack traces.
• DSNs come from env vars — SENTRY_DSN (desktop main, baked in at build by gen-sentry-dsn.cjs), VITE_SENTRY_DSN (desktop renderer), EXPO_PUBLIC_SENTRY_DSN (mobile). All are optional; see the .env.example files. Community and self-built binaries ship without DSNs, so Sentry is a complete no-op and no telemetry is ever sent.

Contributing

Pull requests welcome. See CONTRIBUTING.md for setup, code style, and the PR process.

Security

Found a vulnerability? Follow the disclosure process in SECURITY.md — please don't open a public issue.

License

Apache-2.0 © AlterSend