Barrier is a free, open-source software KVM tool that lets you control multiple computers — Mac, Windows, and Linux — using a single keyboard and mouse, sharing your clipboard across all of them without any extra hardware.
What is Barrier?
Barrier is a software-only keyboard-video-mouse switch: you designate one machine as the server and the rest as clients, and your cursor glides from screen to screen as if you were using a single extended desktop. No USB switcher box, no dongle, no second keyboard collecting dust — just your local network and a small background daemon on each machine.
It is a community-maintained fork of the older Synergy 1.x codebase, kept alive after Synergy moved its latest features behind a paid tier. That heritage means Barrier is battle-tested across a remarkably wide range of operating systems and hardware configurations.
What does Barrier do best?
Barrier's superpower is frictionless cross-platform cursor sharing with a clipboard that actually works — copy text or an image on your Mac, paste it on a Windows machine sitting next to it, and it just works. I run it daily between an M-series MacBook Pro and a Windows development PC, and the latency is imperceptible on a wired or 5 GHz Wi-Fi network.
- Cursor teleporting: configure screen edges in the GUI and your pointer flows naturally between machines as if beaming through the monitor bezel.
- Shared clipboard: plain text and rich text sync bidirectionally; images work between most OS pairings.
- Hotkey to lock cursor: a configurable keystroke keeps the mouse trapped on one machine when you need precision — handy for gaming or video scrubbing on a secondary display.
- TLS encryption: traffic between server and clients can be secured with auto-generated certificates, so your keystrokes are not drifting around your LAN in the clear.
- Scroll direction normalisation: Mac natural scrolling and Windows traditional scrolling can coexist without either machine feeling wrong.
Is Barrier free?
Yes — Barrier is completely free to download, use, and modify. It is released under the GNU General Public License, meaning the source code is public and community contributions are welcome on GitHub. There is no paid tier, no nag screen, and no feature locked behind a subscription.
If you have used Synergy and balked at its annual subscription for TLS and clipboard features, Barrier is the community's answer: all of those capabilities, free, forever. The trade-off is that development moves at a volunteer pace, so don't expect rapid point releases.
Who should use Barrier?
Barrier is built for anyone who genuinely operates two or more physical computers simultaneously — not virtual machines, but separate boxes with their own displays. Developers who keep a Mac for creative work alongside a Windows machine for enterprise compatibility, sysadmins who bounce between a personal laptop and a server console, or streamers who run a dedicated capture PC next to their gaming rig are all perfect candidates.
It is not the right tool if you only need to share a monitor (use a hardware display switch), if both machines are Macs (Universal Control via Continuity is more polished and zero-config), or if you need sub-millisecond input latency for competitive gaming — the network hop adds a few milliseconds that most people never feel but a pro gamer would.
How does Barrier compare to Synergy and Mouse Without Borders?
Synergy is Barrier's upstream ancestor: Synergy 3.x is a paid product ($29–$39 one-time at the time of writing) with a more polished GUI and active commercial support. If you want official builds, a clean installer, and a support ticket system, Synergy is the safer enterprise choice. Barrier is better if your budget is zero and you are comfortable compiling from source or using a Homebrew Cask build.
Mouse Without Borders is Microsoft's free alternative, but it only runs on Windows — useless the moment a Mac enters the mix. Barrier's genuine cross-platform reach (macOS, Windows, all major Linux distributions) is its clearest differentiator. Apple's own Universal Control is the most seamless option between Apple devices, but it cannot include a Windows machine in the chain.
What are the best Barrier alternatives?
For an honest comparison: Synergy (paid, more actively maintained), Apple Universal Control (Apple-only but magical), Mouse Without Borders (Windows-only, free), and Input Leap — another active fork of the same Synergy 1.x lineage that some users prefer for more frequent releases. Input Leap in particular is worth a look if you find Barrier's development pace too slow, as it has diverged with additional bug fixes and maintains a more active pull-request queue.
