How To Duplicate The Screen On Mac - Nektony

Troubleshooting screen mirroring on Mac

If mirroring doesn’t work or something seems off, don’t worry. Here are the most common issues and how to fix them:

My external display isn’t showing up at all

• Check the cable and portMake sure the cable is securely connected and compatible with your Mac and display. Try using another port if available (e.g., a second Thunderbolt/USB-C port). The difference between modern USB-C/Thunderbolt standards also adds to confusion on forums.
• Use a different adapter or hubIf you’re using a USB-C to HDMI adapter, test another one. Some hubs might also not support adapters or be incompatible with some Macs, as stated in this Reddit thread’s comments.
• Force macOS to detect displaysIn System Settings → Displays, press and hold the Option (⌥) key and click the Detect Displays button that appears.

The display is detected, but I don’t see the same image

• Try toggling mirroring off and back onSometimes simply turning mirroring off, waiting a few seconds, and re-enabling it helps reinitialize the connection.

The mirrored screen has black bars or scaling issues

• Adjust resolution settingsIn the Displays section of System Settings, click Advanced → Show resolutions as a list and try a different resolution that matches your external display.

  In some cases, you might even want to toggle Show all resolutions at the bottom of the resolutions list to eliminate scaling artifacts or black bars.

  

• Check the aspect ratioSome projectors or TVs might stretch or crop the image. Look for display settings on the external device itself. For example, on my decade-old Toshiba TV, I need to switch from “Zoom” to “Original” mode every time to see the screen uncropped.

There’s no sound on the external display

• Manually switch audio outputGo to System Settings → Sound → Output and select the name of your external display (e.g., LG TV, Epson Projector). macOS sometimes doesn’t auto-switch.

Also Read:How to do split screen on a Mac