These programs that allow you to share keyboard and mouse input across multiple computers over the LAN, without requiring any additional hardware. Input sharing fills a certain niche that might not be covered entirely by a KVM switch or remote desktop.
I’ve only had experience with Synergy, but I hope to try out the other ones when I have some time and a use case to test them out.
Synergy
When everything is working correctly, Synergy lets you control Windows / Mac / Linux machines from a single system over your LAN. Sharing input across different operating systems is not an easy task though, and sometimes problems happen that require restarting the service and/or entire systems.
I think overall stability has gotten better since I last tried it a few years ago. There are sometimes conflicts with mouse input in games — here is a Github thread on some known issues. Behavior is more predictable in a serious work environment.
Synergy’s licensing and status is a little confusing. There used to be a free and a premium/pro version, but now, my understanding is that it’s technically open-source and free, but Windows binaries are behind a paywall. You can build from source however — I think?
Note: My Synergy version is 1.7.6.
As said above, I have not tried the programs below, but I keep track of them in case I have a use case for Windows-only input sharing.
Mouse Without Borders
Microsoft’s Mouse Without Borders provides input-sharing across up to four Windows systems.
Input Director
Input Director seems to get favorable comparisons against Synergy if you only need to control Windows machines. Will add any thoughts if I have a use case for it. Free for non-commercial use.
Multiplicity
Multiplicity is Windows-only and paid software.
ShareMouse
ShareMouse works with Windows and Mac. There are free and paid versions.
(e:10/Jun/2017: Wording)
