Updating to the latest version of macOS, or running the beta version of Mojave on your Mac, doesn't have to be an all-or-nothing affair. It's possible to install two different operating systems on your Mac and dual-boot them, which means they're both available and you can choose the one that suits you on a day-by-day basis.

In this article we explain how to set up a dual-boot on your Mac, but first you might like to know the benefits that this offers. (For OS options beyond macOS, you might like to read our guides showing How to install Windows on a Mac, and How to install Linux on a Mac.)

Why dual-booting macOS is a good idea

There are a few reasons why you might want to run two versions of the Mac operating system:

  • If you want to update your Mac to the latest software but you have legacy apps that may not run on it. For example, when macOS Mojave launches later this year a number of 32-bit apps will stop working, for example, creating a dual boot could be a good solution if you need to run those apps. Read about which apps won't work in Mojave here.
  • If you're a software developer and need to test your own apps on different versions of macOS (particularly if you need to do this regularly).
  • If you want to safely try out a beta version of the Mac operating system without committing to it (or risking it causing problems with the apps and data on your Mac).

How to dual-boot two versions of macOS

In brief, here's how to set up your Mac so you can run two versions of the macOS operating system on it:

  1. Back up your Mac.
  2. Partition your hard drive.
  3. Install the older version of macOS (or Mac OS X) in partition 1.
  4. Restore your Time Machine backup to that partition.
  5. Install the newer version of macOS in partition 2.

Read on for more detail about each step.

Back up your Mac

This is the first step because when you partition your Mac you will have to completely wipe it.

If wiping your Mac sounds like too much hassle to you, you could try installing the alternate version of MacOS on a external hard drive instead. We show you how here: How to run macOS from an external hard drive.

If you want to keep your current work, you need to create a backup of your Mac and ensure it will fit on your smaller partitioned drive. We show you how to create a backup of your Mac here.

Partition your hard drive

The next step is to create the partition.

You can partition the main hard drive into two separate drives and then install macOS High Sierra on one and a different version of the MacOS on the other. This could be the latest Mojave beta, if you are on the beta program.

In a separate article we explain how to partition your Mac hard drive or SSD.

Alternatively, create your partition by following these instructions:

  1. Boot macOS into Recovery mode (start up your Mac and hold down the Command and R keys until you see an Apple logo or spinning globe).
  2. Once in Recovery mode, use Disk Utility to wipe the main hard drive and split it into two partitions.

Install the old version of macOS in partition 1

  1. Use the Install option in Recovery to install macOS High Sierra (or whichever version you wish to run) on to the main partition.
  2. Recover your Time Machine backup into that partition.

How to dual-boot two versions of macOS: High Sierra

Install the new version of macOS in partition 2

Follow the steps above to install the second version of macOS, or the beta of the new version of macOS, on to the second partition.

Read about how to get the macOS beta here. We also have advice about downloading older versions of macOS here.