Tether brings iMessage, SMS and clipboard sync from an iPhone to Linux

Developer Zack Bartel has published Tether, an open-source project that brings parts of Apple's Continuity features to Linux for people who use an iPhone. Bartel, who moved to Linux full time and wrote about the switch, says Continuity — messaging, notifications, clipboard and file sharing between an iPhone and a computer — was the one capability he genuinely missed.

What the project covers

Tether is distributed under the MIT licence as a Linux daemon named tetherd together with an iOS companion app, Tether — Linux Companion, available on the App Store. It started with clipboard synchronisation between macOS and Linux on Wayland, then added file transfer. Traffic between the two sides has used mutual TLS since the first release, so both devices must authenticate before anything is exchanged, and the author reports regular security reviews of the codebase.

Implementing all of Continuity on Linux is not technically achievable, Bartel writes, so the goal is to cover as much of it as can be done. KDE Connect addresses similar ground but targets Android, and its roadmap did not include the iPhone, which is part of why the project exists.

One-time codes, then Bluetooth

Autofill of one-time passwords was handled with WebExtensions rather than native integration: a browser extension for Firefox and Zen Browser watches for OTP input fields, while a companion extension for Thunderbird and Betterbird reads codes from email and passes them over, so a code that arrives by mail is filled into the login page automatically. The approach works well with those clients but leaves other mail applications unsupported for now.

The harder problem was reaching iMessage and SMS without a Mac. Bartel had tried running a proxy on a Mac and describes the experience as unpleasant even over a VPN. He later found the ancs4linux and BlueFerry projects and credits BlueFerry's protocol documentation with explaining what actually happens on the wire. Both are GPL-licensed while Tether is MIT, so he wrote a clean-room implementation in C++ instead of reusing their code. Bluetooth development, he notes, remains difficult in 2026, with edge cases that had to be tracked down one by one.

Current state

Tether now handles iMessage, SMS, notifications and contact sync on Linux, alongside its earlier file transfer, clipboard sync and OTP handling; text codes sent by message finally autofill in the browser. The project is published on GitHub, and its author, who says he gets nothing from adoption beyond knowing the tool is useful, is asking for bug reports, feature requests, translations and documentation contributions.