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Swapping or remapping modifier keys (Ctrl, Command, Alt Gr)

Updated

Written for Synergy 3 (v3.7.2) and Synergy 1 (v1.21.4), checked 3 October 2026.

To change what a modifier key does on one of your computers, remap it for the computer whose keys you want to change. For example, when sharing a Windows keyboard with a Mac, using the hotkey for copy, Command+C, can be tricky because the Windows key is in a different place than the Command key on a Mac; swapping Ctrl and Super on the Mac fixes that.

A remap changes the keys on that computer only, and only while another computer controls it. Remapping the primary computer (the server) has no effect unless it becomes a secondary computer (a client).

If you swapped two of the Command, Option and Control keys in macOS and they arrive swapped on the computers your Mac controls, remap each of those computers instead of the Mac. The pair to set for each swap is listed under: Keep a macOS key swap on the Mac only

Synergy 3

  1. Open Synergy 3.
  2. Go to Screen layout.
  3. Click the ⋯ menu on the computer whose keys you want to change (for example the Mac).
  4. Click Computer preferences.
  5. Go to the Modifier keys tab.
  6. Set Super to Ctrl.
  7. Set Ctrl to Super.
  8. Click Save.

Each key can become Shift, Ctrl, Alt or Super, and each can be used only once: until you've set both keys of a swap, Synergy 3 shows The right column has duplicates. To remap to Meta as well, first switch on Enable meta key (not the start or command key) in Miscellaneous.

Synergy 1

  1. Open Synergy 1 on your server computer.
  2. Click Configure Server.
  3. On the Computers tab, double-click the computer whose keys you want to change (for example the Mac). The Computer settings window opens.
  4. Under Modifier Keys, set Super to Ctrl.
  5. Set Ctrl to Super.
  6. Click Save.
  7. Click OK to close Server Configuration. If Synergy 1 is running, it restarts with the new configuration.

In Synergy 1, Shift, Ctrl, Alt, Alt Gr, Meta and Super can each be set to any of those keys or to None.

Keep a macOS key swap on the Mac only

If you swapped two of the Command, Option and Control keys in macOS and they arrive swapped on the computers your Mac controls, swap the matching pair back on each of those computers in Synergy 3 or Synergy 1.

To see which keys you swapped:

  1. On the Mac, open System Settings.
  2. Click Keyboard in the sidebar (you may need to scroll down).
  3. Click Keyboard Shortcuts.
  4. Click Modifier Keys in the sidebar.

Then follow the Synergy 3 or Synergy 1 steps above, but choose each computer your Mac controls (for example the Windows computer) instead of the Mac, and set the pair for your swap:

  • Command and Control swapped in macOS: set Ctrl to Super and Super to Ctrl (Super is the Windows key).
  • Option and Control swapped in macOS: set Ctrl to Alt and Alt to Ctrl.
  • Option and Command swapped in macOS: set Alt to Super and Super to Alt.

If you set a swap for the Mac itself while trying to fix this, set each of those keys back to itself (for example Ctrl to Ctrl and Super to Super). Left in place, it swaps those keys whenever another computer controls the Mac. It can't fix this problem, because that's the only time a remap for the Mac applies.

The swap reaches your other computers because Synergy 1 and Synergy 3 read the Mac's keys after macOS has swapped them, and send Command as Super, Option as Alt and Control as Ctrl.

Fix Alt Gr on another computer

If Alt Gr stopped typing characters on a Windows computer you control after an update, update every computer instead of remapping: International keyboards and keyboard language sync

If Alt Gr (the right-hand Alt key used to type accented and other alternate characters) still does nothing on the computer you control, or acts as Alt or left Alt, try the remap below.

Synergy 3

  1. Go to Keyboard & mouse.
  2. Switch Alt Gr for PC keyboards only off (or on, if it was off).

It's on by default, and while it's on, Alt Gr on a PC keyboard acts as Alt on your other computers. The setting is explained in: Keyboard and mouse settings in Synergy 3

Synergy 1

  1. Open Synergy 1 on your server computer.
  2. Click Configure Server.
  3. Double-click the computer where Alt Gr misbehaves.
  4. Under Modifier Keys, set Alt to Alt Gr.
  5. Click Save.
  6. Click OK.

If that doesn't help, set Alt back to Alt and set Alt Gr to Alt instead. In a text config file, the same remaps are alt = altgr and altgr = alt under the client in section: screens. For the file format, see: Creating and using text config files

If the right Alt key on a Linux server sends Alt Gr when your client expects right Alt, see: Keycode or key combinations don’t match

Check your changes

Once you have made the changes, it can be helpful to open up the on-screen keyboard to see how the changes you have made are reflected on the client.

On Windows, it's called the On-Screen Keyboard, and Microsoft explains how to open it: Use the On-Screen Keyboard (OSK) to type

On macOS, it's called the Accessibility Keyboard, and Apple explains how to turn it on: Use the Accessibility Keyboard on Mac

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