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Synergy combines your desktop devices together in to one cohesive experience. It's software for sharing your mouse and keyboard between multiple computers on your desk. It works on Windows, macOS and Linux.
SpecsUpdate
Pros
Pro Works on Windows, macOS, and Linux
Share one mouse, one keyboard, and one clipboard between multiple Windows, macOS, and Linux computers.
Pro Great customer service
After purchasing a professional license with an affiliate code, there's a possible issue where you only have rights to the second version. You can contact customer service and they will respond quickly to add your professional license.
Pro SSL network encryption
Uses SSL network encryption which is especially important since the shared keyboard data may contain passwords, and the application can "control your computer" (as the MacOS X permissions dialog puts it) it is important to ensure that the connection between computers is secured so that even if you are using it on an open WiFi hotspot, others cannot see the data being sent, nor can they inject data into the connection.
Note: This feature is only included with Synergy Pro and all paid versions of Synergy 2.
Pro It was like not having 2 computers but made you feel as if you had one computer with extended monitor
Pro Core software is complete open-source and free
If you know how to compile code from source, you can follow the documentation to compile the core binaries (server and client) and run them on your machines without a GUI using a hand-crafted configuration. Given how seamlessly and beautifully this works on a LAN, the paid option is more of a convenience that helps contribute to FOSS. The model is similar to Xchat and does not bar you from using the full-featured version.
Pro You get to use your favorite keyboard and mouse for all the machines you deal with
Cons
Con Lacks many features of the competition
No Drag & Drop of files. Clipboard sharing is just plain text. No pics. No text formatting.
Con Paid binaries
While being partially open source, Symless charges for builds of their binaries, which is allowed by the GPL (open source license). Cost of $29 for Synergy Basic, or $39 for Synergy Pro. Older versions of the binaries are available for free, and the source code for the core of the app can be downloaded and compiled manually.
Con Clicks don't get transferred to clients when the server is Windows
Bug's been open forever. Still not fixed.
Con No wake-on-lan option for notebooks
This is more of a hopeful suggestion rather than a con, but they currently do not have the "waking-on-lan" feature to power up a notebook in closed position, but they do have plans to include that feature for future upgrades. Some users are definitely looking forward to that feature being available.
Con AltGr key (right Alt/Option key) does not work
This is an old bug they have had for many years and it can be very problematic for people who use keyboard that need that key a lot.
Con Scrolling in Chrome on Mac client is jittery
For some users, there is a bug which causes jittery movement on client. Scrolling on the server is normal.
Con Doesn't work with Mac (as server) with secure keyboard entry
If you use the Mac as the "server", the mouse will switch to the "client" computer but not the keyboard. Simply entering a password in Chrome on the Mac will enable the SecureEventInput and kill the ability to use the keyboard on a Synergy client. The Synergy client doesn't notify the user if this setting is enabled or not.
Recommendations
Comments
Flagged Pros + Cons
Pro I get to use my favorite keyboard and mouse for all the machines I deal with.
Con Randomly works
Have to uninstall and reinstall with every start up each morning and then sometimes it will work.
Out of Date Pros + Cons
Con It stops working randomly on Linux
There is a known bug which Symless are working on where it may stop working randomly when using Linux as a client. They are working on a fix, and it’s due imminently. https://symless.com/synergy/help/known-bugs
Con Random freezes when moving your mouse to the client side
Sometimes the mouse and keyboard freezes in Synergy 1 for 10-30secs randomly, and won't stop until you restart the program.
Con Only one computer can act as a host at a time
Only one computer can act as a host at a time, and the mouse/keyboard sharing is one way. So if you have computer at home, and a computer at work and you want to link your laptop to different computers depending on where you are, you need to change the host settings for each location.
Con Limited Support
Support ONLY comes with their Enterprise product. Basic and Pro support is self-service via forums and other users.
Pro Supports file transfer through an easy-to-use drag and drop interface
Synergy can be used for file transfer using intuitive drag and drop interface.
Pro Jailbroken iOS and modded Android support
It's possible to use computer's keyboard and mouse with a jailbroken Android tablet or phone. Available on GitHub: https://github.com/symless/synergy-android-cyanogen
Con Direct support only for enterprise
Support for non-enterprise users is only available through the forums and other public channels. Only enterprise customers get the benefit of one-to-one phone and email support.
Con Will not install at all
After purchasing Synergy, you might have troubles installing on your Windows 10 PC. Tech support said it's a known bug and will offer refunds.
Con Forever bouncing dock icon that prevents shutdown
Some times causes extra synergy dock icon that bounces forever to appear on mac that cannot be closed or force closed preventing mac from rebooting or shutting down.