Cannot mirror iMac screen to TV over HDMI cable

I'm using cables not wifi to connect to a television screen. I can connect an HDMI cable directly from a 2015 MacBook Pro (Monterey 12.7.6) to any one of three HDMI ports on the tv, and it works fine.


Can't get my iMac (24-inch M3, 2023, Sequoia 15.5) to do the same. I plugged a generic USB-C to HDMI 4K adapter into one of my two Thunderbolt 3 ports in the iMac. Then I took the HDMI cable out of the MacBook Pro and plugged it into the adapter. The TV shows a screen that says "Choose to Mirror or Extend Display from the [ [ ] ] Menu" (the brackets indicate a screen icon). I went to Settings > Displays on the iMac and selected "Mirror Entire Screen" in the control marked "When connected to TV". Nothing happens and the tv still asks "Choose to Mirror or Extend Display ..."


Could the problem be the generic USB-C to HDMI adapter? What should the results be if I used, for example, the Apple USB-C Digital AV Multiport Adapter? Is there anything else I can try?

iMac 24″, macOS 15.5

Posted on May 23, 2025 6:49 PM

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Posted on May 24, 2025 7:51 AM

Good suggestion. My tv (a 2014 JVC model) has four settings: Normal, Wide, Zoom, and Stretch. I tried them all this time. The appearance of the "Choose to Mirror or Extend Display..." menu changed each time, but not picture.


I thought to try my wife's iMac (mine is a 2023 M3, hers is a 2021 M1, both on Sequoia 15.5). When I plugged in the HDMI cable her machine showed a dialog asking what to do. I picked "Mirror" and it showed up on the tv.


I went back to my iMac. I minimized all my windows so a dialog box wouldn't be hidden behind anything. I plugged in the HDMI cable. I saw a new highlighted [[ ]] double screen icon in the upper right corner notification area of the menu bar. I clicked that and then got the same menu. I picked "Mirror" and it showed up on the tv. Yea!


Thanks again for your suggestion. Having something new to try helped me think of other things to try and to be observant of little details that might make a difference.

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Question marked as Top-ranking reply

May 24, 2025 7:51 AM in response to Servant of Cats

Good suggestion. My tv (a 2014 JVC model) has four settings: Normal, Wide, Zoom, and Stretch. I tried them all this time. The appearance of the "Choose to Mirror or Extend Display..." menu changed each time, but not picture.


I thought to try my wife's iMac (mine is a 2023 M3, hers is a 2021 M1, both on Sequoia 15.5). When I plugged in the HDMI cable her machine showed a dialog asking what to do. I picked "Mirror" and it showed up on the tv.


I went back to my iMac. I minimized all my windows so a dialog box wouldn't be hidden behind anything. I plugged in the HDMI cable. I saw a new highlighted [[ ]] double screen icon in the upper right corner notification area of the menu bar. I clicked that and then got the same menu. I picked "Mirror" and it showed up on the tv. Yea!


Thanks again for your suggestion. Having something new to try helped me think of other things to try and to be observant of little details that might make a difference.

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Cannot mirror iMac screen to TV over HDMI cable

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