It’s extremely uncommon for a Mac to freeze or crash these days, but it can happen. What should you do if your Mac locks up and becomes completely unresponsive to the mouse and keyboard? The trick is to press and hold the power button until the Mac turns off. Wait 5 or 10 seconds, and press it again to turn the Mac back on. You will lose any unsaved changes if you do this, so use it only as a last resort when you can’t restart normally. Look for the power button on the back of a desktop Mac, and at the top right of the keyboard on most laptop Macs. For a recent MacBook Air or a MacBook Pro with a Touch Bar, press and hold the Touch ID button.