Last June, Apple announced that it would add external support for external GPUs to macOS. And now, barely a year later, official support has arrived. With the latest update for macOS High Sierra, you can connect a variety of graphics cards to the Mac via a Thunderbolt 3 port and use this extra power to accelerate demanding processes such as gaming and video editing. Apple has specifically highlighted its use for VR.
This should probably not surprise anyone, as it is Apple we are talking about here, but there are a number of limitations to what you can do with external GPUs. Firstly, only selected models are officially supported. And, surprise, Apple only supports some of AMD's Radeon cards, which it already includes in select Macs. This does not necessarily mean that a GeForce card does not work ̵
You can not use external GPUs on Windows through Boot Camp. And just because you have an external GPU connected to your computer when running macOS does not mean that it will not do anything; Developers need to enable support for this. After all, you need a new Mac because external GPUs rely on the super fast speeds of Thunderbolt 3. These include the MacBook Pros 2016 and 2017, the iMac 2017 and the iMac Pro.
If you have a newer machine and use apps that support it, this is a great add-on and, frankly, a surprise from Apple, as external GPUs have become really popular with the gaming community that does not exist on the Mac are. One of the big advantages of Thunderbolt 3 ports is that it provides this kind of powerful flexibility. And now, for those who are willing to spend several hundred extra dollars, they can get a computer that is even more powerful than what they have bought; this could be especially useful for people with MacBook Pros who want a lighter package on the go and more power when plugging in at home or in the office.