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Caps Lock, Num-Lock, and Scroll Lock keys don't act as expected

Updated

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

Operating system: Windows, macOS, and Linux

If Caps Lock, Num Lock or Scroll Lock gets stuck or toggles the wrong way on a computer, turn on the fix for that key on that computer.

Synergy 3

  1. On the Screen layout, click the 3-dots menu on the computer with the problem and choose Computer preferences.
  2. Click the Miscellaneous tab.
  3. Turn on Enable half-duplex caps lock key, Enable half-duplex num lock key or Enable half-duplex scroll lock key, as needed.
  4. Click Save.

Synergy 1

  1. On the server computer, click Configure Server.
  2. Double-click the computer with the problem.
  3. Under Fixes, tick CAPS LOCK key, NUM LOCK key or SCROLL LOCK key, as needed, and click Save.
  4. Click OK. If the server is running, the connection restarts with the change.

If you use a configuration file instead, add any or all of these lines to the screens section, under each screen that has the problem, then restart the server:

halfDuplexCapsLock = true
halfDuplexNumLock = true
halfDuplexScrollLock = true

Why this happens

Some systems treat these keys differently than all the others. Whereas most keys report going down when physically pressed and going up when physically released, on these systems the Caps Lock and Num Lock keys report going down when being activated and going up when being deactivated. That is, when you press and release, say, Caps Lock to activate it, it only reports going down, and when you press and release to deactivate it, it only reports going up. Without the fix, Synergy 1 and Synergy 3 mistake that for a key being held down.