A Mac normally starts from its internal drive, but it can boot from another valid startup disk such as a Boot Camp partition, external macOS drive, bootable backup, or another macOS installation.
This guide applies to Apple Silicon and Intel Macs.
Does This Affect You?
Use these steps when you have more than one bootable system and need either a permanent default startup disk or a one-time boot choice.
Set the Startup Disk Permanently
- Open System Settings.
- Go to General > Startup Disk.
- Unlock the settings with your administrator password if needed.
- Select the drive you want the Mac to start from.
- Click Restart to use it now, or close the window to use it at the next restart.
If the expected drive is missing, confirm it is connected and contains a bootable operating system supported by that Mac.
Pick a Startup Disk for One Restart
Apple Silicon Macs
- Shut down the Mac.
- Press and hold the power button until startup options load.
- Select the disk you want to use this time.
- Click Continue.
Intel Macs
- Turn on or restart the Mac.
- Immediately hold Option.
- Release when bootable disk icons appear.
- Choose the disk and press Return or click the arrow.
Startup Disk Notes
Boot Camp
On Intel Macs, Boot Camp Windows appears as its own startup option. From Windows, the Boot Camp Control Panel can set macOS as the default again.
External Drives Must Be Bootable
A drive with ordinary files will not appear. Apple Silicon Macs also have stricter external boot and security requirements.
Return to Macintosh HD
To go back with certainty, choose the internal macOS disk, commonly named Macintosh HD, in Startup Disk settings.
Startup Disk Is Not Recovery Mode
Startup Disk chooses between installed systems. Recovery Mode is a separate repair environment for reinstalling macOS, restoring backups, or running Disk Utility.
Sources
- Apple Support: Change the disk your Mac starts up from
- Apple Support: Use startup key combinations on your Mac
- Apple Support: Startup Security Utility on Mac