Troubleshooting dual monitor setup on your Mac


NOTE: Most Macs are capable of supporting multiple displays. In order to use an external display with your Mac, plug the display into your Mac using Thunderbolt 3, DisplayPort, or HDMI.

A: Apply all updates

Install all operating system updates and app updates that are available.

B: Check connections on your external displays

B1) Check the connections to your external display(s).

B2) Restart your Mac with the external display connected.

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B3) Adjust the brightness.

TIP: On most Macs, this can be done by pressing the F1 or F2 keys.

B4) If you are using more than one video adapter to connect to your display, try connecting the display with only one adapter.

B5) If your display has more than one video connection, try using a different connection.

C: Check System Preferences

C1) Open System Preferences.

C2) Click Displays.

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C3) Click on the affected display.

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C4) If the display has options for Resolution or Refresh Rate, then match them to your display's manufacturer specifications.

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NOTE: If your display is still not functioning properly, then visit Apple's website at for more information.