When you install the macOS Mojave beta on a separate volume of your hard drive, you can conveniently switch between Mojave and High Sierra on the same Mac, as if each were on a separate drive. And because the storage space used by the additional APFS volume is shared with your existing volume, you don't need to reserve space for the new volume. Its size automatically adjusts to fit your content.
What you need
To complete these steps, you need a Mac that has an all-flash storage device and macOS High Sierra. Make sure that you have at least 20GB of free space to install Mojave, plus any additional space needed for your files and apps. The space required to install Mojave and keep it up to date will vary throughout the beta release period.
Check About This Mac to see how much storage space is available, and check for ”Flash Storage” beneath the drive icon to confirm that you're using flash storage:
Choose Apple () menu > About This Mac, then click Storage.
If your Mac isn't using flash storage, you can create a new partition instead. In that case, follow the steps to add a volume to a device formatted as Mac OS Extended before continuing.
Back up your Mac
Beta software is software that is still in development, which means some apps and services might not work as expected. So it's important to back up your Mac before continuing. You can use Time Machine to make a backup.
Add an APFS volume
- Open Disk Utility, which is in the Utilities folder of your Applications folder.
- In the sidebar, select your existing APFS volume.
- Choose Edit > Add APFS Volume from the menu bar, or click in the Disk Utility toolbar. These options are available only when an APFS volume is selected.
- Type a name for the new APFS volume, then click Add:
Enroll your Mac and install the beta
Go to beta.apple.com and follow the instructions to enroll your Mac in the Apple Beta Software Program, download the Mojave beta installer, and begin installation.
When you're asked to choose where to install the beta, click Show All Disks and choose the volume you just created:
Switch between Mojave and High Sierra
After installation is complete, you can use Startup Disk preferences or Startup Manager to quickly switch between Mojave and High Sierra:
- Choose Apple () menu > Startup Disk, then click and enter your administrator password. Select the Mojave or High Sierra volume, then click Restart.
- Or press and hold the Option key during startup, then choose the Mojave or High Sierra volume when prompted.
Keep the beta up to date
When your Mac is enrolled in Apple Beta Software Program, you will receive a notification when a new public beta is available. To check for updates or install the latest version, use the Software Update pane in System Preferences:
Choose Apple () menu > System Preferences, then click Software Update.