What is AlterSend?
AlterSend sends files between devices over a local network or the internet without uploading them to cloud storage. Desktop and mobile apps support sending and receiving, while a receive-only browser client lets recipients download through a share link without installing the app. Transfers start through a join code or QR code, and trusted devices can be paired for subsequent exchanges without entering another code.
Peer discovery uses Hyperswarm, and connections are end-to-end encrypted with Noise. Files stream in chunks directly from the sender's disk to the receiver, with BLAKE2b integrity checks and support for resuming interrupted downloads. When direct connectivity is unavailable, a relay can forward the encrypted stream without reading file contents. Browser receiving uses a WebSocket relay to reach the peer network.
The application is distributed under the Apache-2.0 license, with installers for Windows, macOS, Linux, iOS and Android. Direct peer-to-peer transfers have no stated file-size limit, but transfers are capped at 10,000 files and relayed sessions have forwarding limits. The release notes also describe a Pro tier using anonymous account codes.
AlterSend screenshots
Explore the interface. Open a screenshot to view it at full size.
Source: official AlterSend project page.
Key capabilities
- Encrypted transfer Files travel over Noise-encrypted connections, with BLAKE2b checks for individual chunks.
- Browser receiving Recipients can download through a share link in a receive-only browser client without installing the app.
- Device pairing Trusted devices can be remembered, with private device keys protected by the operating system keychain.
- Transfer recovery Chunk-based downloads can resume after interruption, and mobile transfers support background operation with platform-dependent limitations.
- Relay connectivity Encrypted relay forwarding provides a fallback when direct connections fail, with custom relay support documented in the release notes.
- Cross-platform apps Native installation options cover Windows, macOS, Linux, iOS and Android.
Where AlterSend fits
AlterSend fits file handoffs between computers and phones, exchanges with recipients who only need a browser, and repeated transfers between paired devices. It provides a transfer path rather than a cloud repository, so workflows should account for the sender remaining available during delivery.
Before deployment, teams should test direct and relayed connections on their networks, particularly with restrictive NAT or VPN configurations. They should also check relay forwarding allowances, mobile background behavior, client protocol compatibility and the file-count cap. Browser receiving depends on relay infrastructure even though file contents remain end-to-end encrypted.
Install
brew install --cask altersendReviews of AlterSend
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