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I have an iMac from 2019 running Catalina that I want to connect to an iMac 2013 running High Sierra as an external display. I bought the cord, but the target display won't work. What am I potentially doing wrong?
iMac Line (2012 and Later)
Use your iMac as a display with target display mode - Apple Support
Are you using a Thunderbolt cable (Lightning bolt icon on the plugs)?
Apple Thunderbolt Cable (0.5 m) - White - Apple
https://www.apple.com/shop/product/MD861LL/A/apple-thunderbolt-cable-20-m
For the 2018 iMac you will also need a Thunderbolt 3 adapter.
Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter - Apple
A. Mini DisplayPort cable won't work, even though the plugs will fit.
Use your iMac as a display with target display mode - Apple Support
Are you using a Thunderbolt cable (Lightning bolt icon on the plugs)?
Apple Thunderbolt Cable (0.5 m) - White - Apple
https://www.apple.com/shop/product/MD861LL/A/apple-thunderbolt-cable-20-m
For the 2018 iMac you will also need a Thunderbolt 3 adapter.
Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter - Apple
A. Mini DisplayPort cable won't work, even though the plugs will fit.
But you said Catalina does not support Target Display. Are there any alternative free software or ways to be able to do dual display? It's dumb Apple would create software to prevent their computers from being used as external displays...
Catalina is OK on the source computer (2019).
Use your iMac as a display with target display mode - Apple Support
More likely Catalina do not support Target Display is the reason.
What software level is required then? Any idea how to downgrade software?
Target Mode with iMac 2019 to iMac 2013 Not Working
