How to Fix It When a Mac Is Not Detecting an External Display

This article offers tips on the display settings and cable specifications to check to fix an issue with a Mac not detecting an external display.

How to Troubleshoot Mac Display Issues

If your Mac is not detecting an external display, follow these steps to troubleshoot and resolve the issue:

1. Check Power Connection:
   • If you’re using a MacBook, ensure it’s connected to power, as certain power-saving settings may restrict external display detection to conserve battery life.
2. Verify Display Support:
   • Check if your Mac supports multiple external displays. Navigate to Apple Menu > About This Mac > Support > Specifications > Graphics and Video Support to confirm.
3. Inspect Cable Connections:
   • Ensure that all cables connecting your Mac and the external display are securely plugged in. If using an adapter, verify its compatibility with your Mac model.
4. Restart External Display:
   • Try unplugging and replugging the display cables or restarting the external display to refresh the connection.
5. Update Adapter Software:
   • If using a dock or adapter, visit the manufacturer’s support site to download any available driver updates.
6. Adjust Resolution Settings:
   • Navigate to System Preferences > Displays and select the “Scaled” option. Hold down the Option key to reveal the “Detect Displays” button and click it to scan for connected displays.
7. Experiment with Resolutions:
   • Try selecting different resolutions under the “Scaled” option to prompt a change in display behavior.
8. Disable Automatic Brightness Adjustment:
   • Uncheck the “Automatically adjust brightness” option and manually adjust the brightness using the toggle if the display appears too dim.
9. Sleep and Wake Mac:
   • Put your Mac to sleep briefly and then wake it up to see if the display is detected.
10. Restart Mac with Display Connected:
    • Restart your Mac while the external display is connected to see if it is recognized upon reboot.
11. Perform Hard Reset:
    • Disconnect all cables, power off both your Mac and the external display, wait for a few minutes, then reconnect and power them back on.
12. Avoid Daisy-Chaining Adapters:
    • Minimize the use of multiple adapters and cables connected in series, as this may lead to compatibility issues.

If the problem persists, it could be due to incompatibility between the Mac and the monitor, faulty or incorrect cables, power-saving settings, outdated drivers, or incorrect display preferences. By following these troubleshooting steps, you can identify and address the issue preventing your Mac from detecting the external display.