Target display mode Question

It should definitely work as according to Apple that is what is needed besides the Target Mac running 10.13.6 or less...

You can connect any of these older iMac models to another Mac from 2019 or earlier for use as an external display. Learn how to identify your iMac model.

• 27-inch iMac models introduced in 2009 and 2010: Use a Mini DisplayPort cable to connect your iMac to a Mini DisplayPort or Thunderbolt or Thunderbolt 2 port on the other Mac.
• All iMac models introduced in 2011, 2012, 2013, and mid 2014: Use a Thunderbolt cable to connect your iMac to a Thunderbolt or Thunderbolt 2 port on the other Mac. If the other Mac uses Thunderbolt 3, you can use the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter with your cable.

Target display mode requires macOS High Sierra or earlier on the iMac used as the external display. It does not work with macOS Mojave or later.

You need a USB-C to Mini DisplayPort Cable, such as:

https://www.startech.com/AV/display-and-video-adapters/usb-c-video-adapters/usb-c-mini-displayport-cable~CDP2MDPMM1MB

The USB-C end plugs into one of the MacBook Pro's Thunderbolt 3 ports.

It appears that Apple disabled this feature in newer Macs, at least in the 2019 MacBook Pro 16".

I have a 2011 27" iMac (running 10.13.6) that is advertised as being able to be used as the display in target display mode. I'm using a mophie USB-C Cable with Mini DisplayPort Connector (sold by Apple) to connect to the iMac from a Late 2019 MacBook Pro 16". But target display mode isn't happening, even if I type Command-Fn-F2 or Command-F2 on the iMac as per the Apple target display mode page: https://support.apple.com/en-us/HT204592. The MBP is running 10.15.6.

Does anyone have target display mode working from a 2019 MacBook Pro 16"?

Is it possible that I need the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter plus a Thunderbolt 2/Mini DisplayPort cable?

You need a mini display port cable to connect to the iMac. Use your iMac as a display with target display mode - Apple Support

It did not work, he needed 10.13.6 or earlier on the MBA. My recommendation to the OP and you is to buy an external display, otherwise you are wasting your time.

Unlike the 2009 iMac, the 2011iMac uses Thunderbolt, not Mini DisplayPort.

For a 2019 Mac to use a 2011 iMac as a display you need a Thunderbolt 3 adapter

Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter - Apple

and a Thunderbolt cable.

Apple Thunderbolt Cable (0.5 m) - White - Apple

A USB-C/Mini DisplayPort cable won't work, even though the plugs will fit.

Great, thanks, now I get it. I had thought there was some compatibility with a Mini DisplayPort cable, but clearly there isn't, as it isn't working for me with the mophie cable. I have the adapter, so I'll get a thunderbolt cable.

Can you please let us know what worked for you?

The iMac being used as a display must have 10.13.6 or earlier, but there is no such restriction for the other computer.

Is it possible that I need the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter plus a Thunderbolt 2/Mini DisplayPort cable?

Yes, was just getting ready to post just that.

Are you saying it is necessary and sufficient to use Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter plus a Thunderbolt 2/Mini DisplayPort cable?

Or are you just saying maybe that will work?

👍