The right cable for Migration Assistant over Thunderbolt with Target Disk Mode

So yesterday it took me a while to figure out how to use Target Disk Mode over Thunderbolt to transfer data from an older MacBookPro to a new one. So I thought I would write it down for the next person figuring this out.

You will need a proper Thunderbolt 3 to Thunderbolt 3 cable. Apples doesn't sell one. Just having a cable that has USB-C plugs on both ends doesn't work.

If the old Mac has Thunderbolt 2 you will need a Thunderbolt 2 to 3 adapter, which Apple sells and a Thunderbolt 2 cable.

To boot in Target Disk Mode shut down your Mac. Then turn it on while holding the key t until you see a Thunderbolt icon on the screen.

Start Migration Assistant on the other Mac and connect both with the Thunderbolt cable.

Data should be completely copied over in a few hours at most.