How to use one monitor with two Macs simultaneously?

If your monitor has 2 HDMI inputs you could connect both Macs and then in your monitor flip back & forth between the inputs.

Another possible option (assuming both Macs are on the same network) would be to set up your old Mac using your HDMI Monitor and enable Screen Sharing on your old Mac. Then shut down, disconnect the HDMI monitor and connect an HDMI Dummy Plug to the old Mac. Connect the HDMI monitor to your new Mac and open a Screen Sharing session to your old Mac. If you want to try this option, make sure whatever HDMI Dummy Plug you get supports the resolution of your monitor.

Here is a better wording of my previous post (I ran out of editing time on my previous post).

Another possible option would be to enable your old Mac to run "headless" and use File Sharing or Screen Sharing -

• Use File Sharing if you just want to "see" and manage files & folders on the old Mac from your new Mac
• Use Screen Sharing if you want to "see" the display of the old Mac and operate the old Mac from your new Mac

• Set up your old Mac using your HDMI Monitor with it.
  • Enable File Sharing and Screen Sharing on your old Mac.
  • Shut down the old Mac, power off and disconnect the HDMI monitor.
  • Connect an HDMI Dummy Plug to the old Mac. This enables your old Mac to run "headless."
• Make sure both Macs are connected to the same network. Wired is highly preferred for Screen Sharing.
• Restart the old Mac.
• Connect the HDMI monitor to your new Mac.
  • Restart the new Mac
  • On your new Mac, open a File Sharing or Screen Sharing session to your old Mac.

If you want to try this option, make sure whatever HDMI Dummy Plug you get supports the resolution you want to use on your monitor and make sure to set Display Settings in both Macs for that resolution.

Here is an example of an HDMI Dummy Plug. I have not used it, so it's just an example, not a recommendation.

Unless your monitor has multiple video inputs and also has a "Picture in Picture" feature, it will not show signals from two computers at the same time.

Sk1pp1 wrote:

I want to see files on old model whilst also using new one?

Maybe you can clarify what it is you want to "see"... If they're on the same network, you can use file sharing to make all of the data on one available on the other.

I just noticed that you posted your question here in the iMac forum. iMacs each have their own built-in display and they don't have HDMI ports.

Are you actually using mac Minis?