Have you ever noticed that sometimes when you hold down the option key when booting up your Mac, you’ll see both a “EFI” and a “Windows” volume listed? Why do both show up? Which is the correct one to select?

Turns out that the first question is easier to answer than the second. If there is a Windows boot folder on the EFI partition (usually /dev/disk0s1), you’ll see an EFI boot option. If there is a master boot record partition map and a flagged partition, you’ll see the “Windows” option to boot via the MBR method. If you have a new Mac with the latest firmware, it won’t show EFI but will show “Windows” since these new Macs can boot Windows in native EFI boot.

This helps to answer the “which one to select” question. If you have the latest MacBook Air, MacBook Pro, or iMac, and you are booting off the install drive to install Windows, you will see both a EFI and Windows option. If you select EFI, Windows will boot into EFI mode and set the machine to EFI boot. This results in faster boot times and more flexibility (like external drive booting and windows on multiple partitions). If you don’t have a latest Mac, select the “Windows” option and windows will install in the more compatible MBR mode.