Best Free Software KVM (Synergy)

Synergy is a free software KVM for Windows, Linux, and Mac.
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In the past, I would purchase a hardware KVM (Keyboard, Video, and Mouse) to connect multiple computers together. But these days, I'm changed to using a software based KVM. It works slightly differently by allowing multiple computers with their own monitors, to share a single keyboard and mouse in a client/server setup. The keyboard and mouse are connected to a computer dedicated as the KVM server and the mouse seamlessly moves between different monitors from client computers. Additionally, copied text on one machine can be pasted onto the screen of a different computer. Another benefit is it works across different operating systems (Windows, Mac, and Linux). Best of all, this open-source software is free. It's called Synergy!

My Synergy Setup

I have a Windows 10 laptop that I regularly use outside my home at coffee shop or other homes. When at home, I use the laptop monitor plus a connected laptop (via HDMI). My second machine is also Windows 10, but a desktop machine that is always on and servers as a mini-server for other purposes around the house.

  • My Windows 10 desktop is the Synergy "server" because it is always on. So I have my keyboard and mouse connected to the desktop.
  • My Windows 10 laptop is the Synergy "client".

After setup (basically designating the IP address and monitor orientation), the "Synergy" application can be configured to start on boot-up. It is set and forget. Best of all, when my laptop isn't connected, the mouse still works on my desktop machine.

At the end of the day, my one keyboard and mouse works across three monitors from two different Window 10 machines. If I ever purchase another machine, it can be seamlessly added to my setup.

Downloading Synergy

If you Google "Synergy", you'll find results from SourceForge and one by Symless. Symless is a commercial upgrade of SourceForge, but requires an active internet connection to work. Many reviewers have noted Synergy by Symless is slower and does not work as well.

My currently used version of Synergy is the source version that is freely available at SourceForge and the one I use for my dual Windows 10 setup. Note the original open-source application has not been updated since October 2017, but still works well.

Download Synergy v1.8.8 from SourceForge for Windows, Linux, or Mac

If you want to try a newer free version of Synergy, an actively developed (still open source) version of Synergy was created a call Barrier on GitHub. I have not tried Barrier yet because Synergy still works with Windows 10.

Mouse Lag on Synergy Client (Windows 10)

From time to time, the mouse movement on the client lags, but works fine on the server. The mouse and keyboard work fine on the server. It lags to the point where it's usable, but with a lot of patience. The solution:

  1. On the "server", open Task Manager (right click taskbar and select "Task Manager").
  2. Make sure "More Details" is selected on the bottom. You should see a list of tabs at the top of the "Task Manager" window.
  3. Select the "Details" tab on the "Task Manager" window.
  4. Locate "synergy.exe", "synergyd.exe", and "synergys.exe". It helps to make sure the list is sorted by the "Name" column.
  5. Right click each application listed in Step 4, check "Set priority" and set it to "High". There will be a confirmation window, so click "Change priority".

You may be tempted to select "Realtime" in Step 5 above, but doing so may cause the server machine to lag.

Other Software KVM Options

Synergy is not the only option. There are other available software KVM options available. Since Synergy has been working for me since Windows 7, I have not found the need to download and review any of these options. Feel free to try for yourself.

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