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 Fix Mac Display Issues

Try the following fixes, in order, to try to get your Mac to recognize the external display.

1. Double-check your cables. First, ensure your cables are correct and secure. Check that the cords between your Mac and the display are firmly connected and confirm that the display is plugged in.

2. Make sure you’ve got enough power. If you’re using a MacBook, plug it into power. Some power-saving settings may restrict processes to extend battery life, and if your display isn’t receiving enough power, it won’t work.

3. Disconnect and then reconnect your cables. If you’ve already checked your connections and know that your monitor is getting enough power, try unplugging all your cables (including the power cable), wait about 30 seconds, and then plug them back in. Restarting the external display may give your Mac a fresh shot at recognizing it.

4. Make sure your Mac supports more than one additional monitor. Check the supported number of displays by clicking the Apple icon, navigating to System Settings > Help > your MacBook, and reviewing Display Support or Video Support.

   On older macOS versions, click the Apple icon > About This Mac > Support > Specifications > Graphics and Video Support.

5. Ensure that any adapter is compatible. If you’re using an adapter, ensure your monitor and cable combination is compatible with your Mac. Some Macs use only USB-C or both Thunderbolt and USB-C connections, and some Thunderbolt variations require a Thunderbolt-specific adapter.

   In the case of a dock, check its manufacturer’s support site and download new drivers, if applicable.

6. Check your resolution. Check resolution settings by navigating to System Settings > Displays. Press and hold the Option key to reveal a hidden Detect Displays option at the bottom right. Click this button to prompt your Mac to scan for a connected display.

   On older macOS versions, get to this option by selecting System Preferences > Displays > Scaled.

7. Choose different resolutions. While in Resolution settings, Ctrl+click a resolution on the list and choose Show Thumbnails. Select a non-default thumbnail option to see if it prompts a change.

   You may see a radio button next to Scaled. If you do, choose a different resolution from this view.

8. Deselect automatic brightness adjustments. Under Brightness, uncheck the box next to or deselect Automatically adjust brightness and manually brighten using the toggle. If the external display’s brightness is too low to register, this could resolve that issue.

9. Give It a rest for a few seconds. Put your Mac to sleep briefly, then wake it to see if there are changes in the Display preferences.

10. Restart your Mac. Go ahead and restart your Mac, but keep the external display connected. Sometimes this will clear whatever is preventing your Mac from detecting the monitor so when it powers back on, it can complete the connection process.

11. When all else fails, start all the way over. Disconnect all cables, power off your Mac and the external monitor for a minute or two, and then reconnect the cables and turn everything back on. Repeat the steps for the Display settings if the monitor still doesn’t work.

    When you’re going through this process, be sure to reconnect everything before you power your Mac back on. That will ensure that the computer goes through the detection process as it’s powering up, which might help it find the monitor.

Cause of Why a Mac Is Not Detecting an External Display

Problems between Macs and external monitors can stem from various causes, including:

• Incompatibility between the Mac and the monitor.
• Faulty cables (or the wrong cables).
• Power-saving options in a MacBook prevent it from running an external monitor.
• Outdated drivers or software for docks.
• Incorrect settings in your Mac’s Display settings, including brightness and resolution.