Barrier is an open-source software KVM switch written in C that allows users to control multiple computers using a single keyboard and mouse across a network. The project was forked from Symless's Synergy 1.9 codebase, which itself descended from the original CosmoSynergy by Chris Schoeneman. Unlike Synergy, which has evolved into a commercial product with expanded functionality, Barrier maintains focus on the original 1.x era goals of simplicity and reliability for keyboard and mouse sharing with clipboard synchronization support.
The software works by allowing users to move their mouse to the edge of the screen or use keyboard shortcuts to switch control between connected machines. One machine acts as the server with the physical keyboard and mouse, while other machines function as clients. Users configure the server by dragging screen representations onto a grid and ensuring screen names match exactly between server and client configurations. Clients connect by entering the server's IP address or using Bonjour auto-configuration. The experience mimics having a single unified desktop across multiple monitors, though Scroll Lock being active will prevent mouse switching between screens.
Barrier supports Windows 7 through 11, macOS, Linux, FreeBSD, and OpenBSD. The project provides releases for Windows and macOS through GitHub, while most Linux distributions already package Barrier. The team also maintains Flatpak and Snap distributions for broader accessibility. Continuous integration builds are provided by Microsoft Azure Pipelines, Flathub, and Canonical, with separate build status tracking for Linux, Mac, Windows Debug, Windows Release, and Snap platforms.
Known limitations include limited UTF-8 support affecting various language processing, no drag-and-drop functionality on Linux, and lack of Wayland support on Linux as of late 2021 with no expected completion date. The project explicitly states that Barrier is not compatible with Synergy and requires installation on all machines that will share keyboard and mouse. The team prioritizes issues affecting wider user bases and emphasizes open communication through the public issue tracker. Contributions are actively sought, particularly for fixing tracked issues, with pull requests requiring release notes documented in the newsfragments directory. Support is available through the GitHub issue tracker for bug reports and the LiberaChat IRC network in the #barrier channel for questions and community interaction.
