One keyboard multiple PCs: control desktops without a KVM

A software bridge installs a small program on every computer and passes your keyboard and mouse input across the network. A KVM switch (short for keyboard, video and mouse) does a similar job in hardware, but these apps skip the video part: each PC keeps its own monitor, and only the input travels.

Most tools give you two ways to move between machines. In edge mode, you push the cursor past the side of one display and it lands on the neighboring computer’s screen. In hotkey mode, a key combination jumps control straight to another PC. Hotkeys can be faster when your cursor is far from the right edge, but it can take a second to spot where the pointer ended up.

Many of these apps also share your clipboard, so text you copy on one computer can be pasted on another. Some go further and move files.

If every computer on your desk runs Windows, start with Mouse Without Borders. It began as a Microsoft Garage experiment and now ships inside PowerToys, Microsoft’s free bundle of add-on tools for Windows. It links up to four PCs.

Setup is short. You turn the tool on in the PowerToys settings on your main computer and generate a security key. On each extra PC, you type that key plus the main computer’s name and connect. After that, the cursor crosses between screens freely.

Clipboard sharing works for text and images, and you can copy and paste files through File Explorer. Reports differ on dragging: the PowerToys version is described as handling drag-and-drop for files under 100MB, while one hands-on test of the app found dragging between PCs didn’t work. If moving big files matters to you, test it on your own setup first. The original standalone app hasn’t been updated in years, so the PowerToys version is the one to use.

For a desk with a Mac or a Linux box, look at Deskflow and Synergy. They share a family tree. Synergy started as an open source project about 25 years ago, and its developer later turned it into a paid product sold by a company with the same name. Community spinoffs called Barrier and Input Leap tried to keep a free version going, but both fell behind and are now inactive.

Deskflow is the replacement. It is free and open source, and Synergy itself backs it with money and code. It runs on Windows, macOS, Linux and FreeBSD, supports Wayland on Linux, shares the clipboard and switches on TLS encryption (the same kind of scrambling your browser uses for secure sites) by default. It can also talk to older Barrier and Input Leap setups, so you don’t have to replace everything at once.

Both apps work the same basic way. One computer is the server, the one whose keyboard and mouse you actually use, and the rest are clients, usually added by their network address. A grid on screen lets you place each computer to the left, right, above or below the others, which sets the edge your cursor crosses.

A few practical notes for Deskflow:

• Windows needs Windows 10 version 1809 or newer, plus Microsoft’s Visual C++ runtime.
• On a Mac, you must grant accessibility access in Privacy and Security, and on recent macOS versions also local network access.
• Because the Mac app isn’t notarized by Apple, macOS may wrongly call it damaged. The project’s Homebrew package is the easiest way around that.

Synergy charges by how many computers you link: $15 for three, $19 for five and $29 for 15, with separate pricing for businesses. For that, you get automatic discovery of other computers on your network, so you don’t have to type addresses, and stronger tools for IT teams managing many desks. The company has also been previewing a new version called Synergy Dragon with a cleaner look, more accurate monitor layouts and file transfers between connected computers.

One quirk showed up in testing with several laptops: in both Synergy and Deskflow, a client laptop’s own trackpad couldn’t push the cursor back over to the server machine. If you like grabbing whichever trackpad is closest, keep that in mind.

Stardock’s Multiplicity is the other paid choice, again Windows-only. Its Pro version adds tricks the others lack, such as using a second PC as an extra monitor, switching several PCs on one screen and routing one computer’s audio through another’s speakers.

Every one of these tools needs your computers on the same local network. At home or in a private office, that is easy. On public Wi-Fi in a cafe or co-working space, the connection often fails outright, because those networks commonly block devices from talking to each other.

Shaky Wi-Fi hurts too. If the signal drops, the cursor lags or the link breaks until it reconnects. A wired connection for at least the main PC makes things much smoother. None of these apps support Chromebooks, so a ChromeOS machine on your desk can’t join in.

For most people, the choice comes down to three questions:

• All Windows, up to four PCs? Use Mouse Without Borders in PowerToys. It’s free.
• A Mac or Linux machine in the mix? Try Deskflow first, since it costs nothing.
• Want easier setup or many machines? Synergy’s paid plans add network discovery and business tools.