How to Install MacOS Catalina Beta on APFS Volume to Dual Boot with Mojave

If you want to run MacOS Catalina Beta alongside macOS Mojave or macOS High Sierra, you can do so by adding a new APFS volume to the Mac if that Macs hard drive is formatted as APFS. This effectively creates a dual boot scenario for MacOS Catalina 10.15 and Mojave 10.14.x (or High Sierra), and offers an alternative approach to simply installing MacOS Catalina Beta on a Mac as the primary operating system. There are a few advantages to this approach, notably that you can use a single Mac for running the two operating systems, and you won’t need to designate storage capacity for Catalina as it will share the drive space with the other MacOS release and expand as needed.

Important: This is for advanced Mac users only. There are mixed reports of problems with running MacOS Catalina alongside other macOS releases, particularly for Macs with T2 security chips and Touch ID. Be absolutely certain you have a full backup of your data and Mac before attempting this.

To get started, you’ll need a full backup of the Mac and all data on the computer, a Mac compatible with MacOS Catalina, you’ll need to be enrolled in the MacOS Catalina beta testing program, and you’ll need a minimum of 35GB of free disk space available though more is recommended for best results with trying Catalina.

How to Install MacOS Catalina in an APFS Volume Alongside MacOS Mojave / High Sierra

This will create a dual boot environment allowing you to switch between MacOS Catalina and MacOS Mojave or High Sierra.

1. Back up the Mac with Time Machine or your backup method of choice, do not skip this step
2. Open Disk Utility on the Mac and create a new APFS volume by clicking on the “+” plus button
3. Name the new APFS volume something obvious like “Catalina” and click “Add” (optionally you can adjust size options but this is not necessary)



4. Click “Done” and then quit Disk Utility when finished
5. Open the “Install MacOS Catalina Beta” application found in the /Applications folder (you can also use a MacOS Catalina USB boot drive if you made one) and click “Continue” then read and agree to the terms of service
6. Click on “Show All Disks”



7. At the disk selection screen, choose the alternate “Catalina” APFS Volume you created earlier as the target disk, then click on “Install” to install MacOS Catalina Beta onto that volume



8. Let the entire MacOS Catalina installation complete, the Mac will reboot and the process will take a while to finish

When the installation completes and the Mac reboots for the final time, the computer will start directly into MacOS Catalina.

How to Switch Booting of MacOS Catalina or MacOS Mojave / High Sierra

You can switch between booting and running MacOS Catalina and MacOS Mojave or High Sierra by doing either of the following:

Switching Boot macOS Versions on System Start

• Restart or boot the Mac and immediately hold down the OPTION key, then at the boot selection screen choose the macOS volume you wish to boot from

Switching Boot macOS Version via System Preferences

• Pull down the  Apple menu and go to “System Preferences” and then go to “Startup Disk” and choose the volume / OS to boot from

Removing MacOS Catalina APFS Volume

If you wish to remove MacOS Catalina Beta, you can simply open Disk Utility and delete the APFS volume that you created to install MacOS Catalina onto.

Since you are not upgrading or installing MacOS Catalina over an existing MacOS release or as the only operating system on the computer, the typical downgrade Catalina method is not necessary (unless you wanted to format and erase the entire Mac and all volumes, anyway).

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Have you installed and run MacOS Catalina in an APFS volume? Did you use another method? Do you have any particular tips, advice, reports, or experiences you wish to share? Share with us in the comments below!