Detect Displays on macOS

Sometimes when I use an external display with my MacBook Pro in clamshell mode, nothing shows up — I just get a black screen. And when this happens, forcing macOS to “Detect Displays” can help.

To trigger “Detect Displays” on macOS, just hit Command+F2 (brightness up).

You can also do this using the trackpad:

  • Navigate to System Preferences > Displays
  • Hold down the Option key to reveal the Detect Displays button
  • Click Detect Displays

This works in macOS Mojave, and others have reported it works with previous versions of macOS.