If you're using a Mac with Apple silicon, the startup options window appears when you turn on your Mac, then continue to press and hold its power button for at least 10 seconds.
Here's what you can do in startup options:
- Select a startup disk, such as Macintosh HD. Then click Continue to start up from that disk.
- Select Options, then click Continue to open macOS Recovery. From there you can reinstall macOS, use Disk Utility to repair your disk or erase your disk, and more.
- Click Shut Down or Restart.
These hidden features are also available in startup options: