How to Fix an External Display Not Detected on Mac

Step by step

1. 1 min

   Verify physical connection and power

   Ensure the external display is connected to a power outlet and powered on. Disconnect the video cable from both the Mac and the monitor, then firmly reconnect them to ensure a secure seating. If using a hub or docking station, bypass it by connecting the display directly to the Mac to rule out hardware failure in the adapter.

   Note: Verify the monitor is set to the correct input source via its physical OSD menu.
2. 30 sec

   Force the Mac to detect the display

   Open System Settings from the Apple menu. Navigate to Displays, then hold the Option key on your keyboard. A Detect Displays button will appear in the bottom right corner of the window. Click this button to force the operating system to scan for connected hardware.

3. 1 min

   Modify refresh rate and resolution

   Within the Displays settings menu, select the external monitor if it appears in the diagram. Check the Refresh Rate dropdown and select a lower value, such as 60Hz. If the resolution is set to an unsupported mode, toggle it to Default to reset the signal to a standard frequency.

   Note: Unsupported high refresh rates can often cause a blank screen on older cables.
4. 2 min

   Restart the WindowServer process

   Open Activity Monitor from Applications > Utilities. Type WindowServer into the search field at the top right. Select the process, click the X icon in the toolbar, and choose Force Quit. This restarts the graphics management process without requiring a full system reboot.

   Note: Unsaved work will be closed when the WindowServer process restarts.
5. 3 min

   Perform a Safe Mode restart

   Shut down your Mac completely. For Apple Silicon Macs, press and hold the power button until 'Loading startup options' appears, select your disk, hold the Shift key, and click Continue in Safe Mode. This clears system caches and disables third-party display drivers that may be interfering with the connection.