Why do brightness keys stop working when the slider still works?

If the menu slider still adjusts the intended display, first check keyboard handling and target selection. A working slider shows that BetterDisplay can make that adjustment. The next step is to check whether the app receives the key press and sends it to the same display.

  1. Open Settings > Keyboard > Native (Apple) Keyboard Control. Enable Brightness control using native brightness keys and check whether the status says BetterDisplay is listening.
  2. Complete the permission setup offered there, and restart BetterDisplay if the permission sheet requests it. See Native Keyboard Control for the macOS-specific permission route.
  3. Check Brightness Keys, Video Adjustment Shortcuts Affect:. With Screen with the mouse pointer, move the pointer onto the intended screen. Also check that Keyboard control affects this display is enabled for that display. See Target Displays.
  4. If those settings are correct, quit other apps that handle keyboard events one at a time, then retest. Another app can interfere with native-key handling even though BetterDisplay’s slider continues working. If one app consistently triggers the problem, isolate that interaction before changing display-control settings.

If only one brightness key fails, compare it with another keyboard or a separately assigned shortcut before changing display settings. A worn or intermittent key can coincide with an app or macOS update. Confirm that both keys produce an input. If the problem started around an update, this comparison helps establish whether the key itself is still working.

To adjust the built-in and external displays together, choose All suitable screens under Brightness Keys, Video Adjustment Shortcuts Affect: and enable Keyboard control affects this display for each intended display. Every target still needs a working brightness controller. This selects the displays directly and bypasses group brightness synchronization for the key operation.

If you want the MacBook’s brightness keys to retain their ordinary macOS behavior, turn off Brightness control using native brightness keys. If you keep BetterDisplay’s handling enabled, its target preference determines which display receives the adjustment.

A temporary recovery after restarting an app or waking the Mac does not identify the cause by itself. Compare the listening status, selected target and other running keyboard utilities while the problem is present.

For a keyboard that sends ordinary function keys instead of Apple brightness events, check its own function-key mode. BetterDisplay also supports Allow using F14/F15 as alternative brightness keys. The native-key reference explains that option.

For ordinary F1/F2 or other function keys, open Settings > Keyboard > Keyboard Shortcuts… and record them for the desired brightness or volume actions. Assigning a key in macOS System Settings does not create the corresponding BetterDisplay shortcut. If recording or using it fails, check whether macOS or another app already reserves that combination, or choose a different one. See Custom Keyboard Shortcuts.