To use any of these key combinations, press and hold the keys immediately after pressing the power button to turn on your Mac, or immediately after your Mac begins to restart. Keep holding until the described behavior occurs.
If your Mac is using a firmware password, all of these key combinations are disabled, except as noted below.
|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.
If your Mac is using a firmware password, you're asked to enter the password first.
|D||Start up from the built-in Apple Hardware Test or Apple Diagnostics utility, 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.
iMac Pro doesn't support this startup key.
|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.|
|Option-Command (⌘)-P-R||Reset NVRAM (or PRAM).
When using a firmware password, your Mac ignores this combination or starts up from macOS Recovery. To reset NVRAM, first turn off the firmware password.
|Command-S||Start up in single-user mode.|
|T||Start up in target disk mode.|
|Command-V||Start up in verbose mode.|
|Eject (⏏), F12, mouse button, or trackpad button||Eject removable media, such as an optical disc.|