Faster Transfer question

There seems to be a little more to it than just connecting them together. Somebody needs to decide complete the Network information, possibly including what IP addresses to use each end, or use a special mode.

as zarathu suggested you could put one into Target Disk Mode. It used to be only for Firewire, but they have continued to support it using ThunderBolt.

If you have two computers with ThunderBolt-3 ports, you can use a genuine ThunderBolt-3 cable to connect them together. A new Network connection method will appear in System preferences > network, and you can choose it and give it any missing information such as DNS server address. The other Mac will then connect according to this article:

Use IP over Thunderbolt to connect Mac computers - Apple Support

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One of the macs would have to be in Target Mode. I might be wrong, but I don’t think Target has existed for several OS’s.

I couldn’t find any Apple Support references to do this, but maybe one of the old hands here knows how to do it.

When Grant says a Thunderbolt cable, you need an Apple Thunderbolt cable. Anything less and it may not work. It seems to me that doing it with a simple HDD using Time Machine would be much easier, even if you do have to go out for breakfast while it's happening.