Hold during startup | Description |
Shift (⇧) | Start up in Safe Mode. |
Option (⌥) | Start up to Startup Manager, which allows you to choose other startup disks, if available. |
C | Start up from an available CD, DVD, or USB thumb drive that contains a valid operating system for your Mac. Or use Startup Manager, as described above. |
D | Start up from the built-in Apple Hardware Test or Apple Diagnosticsutility, depending on your Mac model. Or use Option-D to start up from this utility over the Internet. |
N | Start up from a compatible NetBoot server, if available. To use the default boot image on the NetBoot server, hold down Option-N instead. |
Option-Command (⌘)-P-R | Reset NVRAM or PRAM. |
Command-R | Start up from the built-in macOS Recovery system. Or use Option-Command-R or Shift-Option-Command-R to start up from macOS Recovery over the Internet. macOS Recovery installs different versions of macOS depending on the key combination you use while starting up. |
Command-S | Start up in single-user mode. |
T | Start up in target disk mode. |
X | Start up from your macOS startup disk when your Mac would otherwise start up from a non-macOS startup disk, such as a Windows partition. Or use Startup Manager, as described above. |
Command-V | Start up in verbose mode. |
Eject (⏏), F12, mouse button, or trackpad button | Eject removable media, such as an optical disc. |
From <https://support.apple.com/en-us/HT201255 >
...