Useful Boot Key Commands

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.

Zap the P-RAM

Safe Boot Mode
Shift (⇧)

Reset the SMC

Target Disk Mode

Recovery Mode

Diagnostic Mode
D or  Option-D (depending on your Mac model)

Specify Boot Drive (and more)

Mac keyboard shortcuts

Keyboard Symbols