How to Run Two Versions of macOS Together

Updating to the latest version of macOS or running a macOS beta on your Mac doesn’t have to be an all-or-nothing affair. It’s possible to install two different operating systems and dual-boot your Mac. This means you’ll have both versions of macOS available and can choose which one works for you on a day-to-day basis.

In this article, we’ll show you how to set up your Mac to dual-boot two versions of macOS, but first, you might like to know what benefits this offers.

Why dual boot macOS

There are several reasons why you might want to run two versions of the Mac operating system, which is essentially what dual booting means:

• If you want to update your Mac with the latest software, but have outdated applications that may not work on it, creating a dual boot can be a good solution if you need to run those applications.
• If you are a software developer and need to test your own apps on different versions of macOS (especially if you need to do this regularly).
• If you want to safely test a beta version of the Mac operating system without committing to it (or risking causing problems with the apps and data on your Mac).

There’s another point of confusion when it comes to dual booting. On older versions of Mac OS X and macOS, you would have had to partition your Mac, while in more modern versions of the Mac operating system, you create a volume. We’ll assume you’re using a newer version of macOS, so we’ll focus on creating a second volume, but we’ll also cover creating a partition separately.

Before you begin…

Before you begin, no matter what version of macOS you’re using, you should know the following:

• Make room: If you want to carve up your Mac so you can run two versions of the operating system, you’re going to need some space. Learn how to free up space on a Mac . So before you start, start deleting. Delete apps you don’t use (here’s how to delete apps ), delete all the files and folders you don’t need, copy your massive photo library to an external drive, think about what you can delete from Other, System, Cache, etc.)
• Backup: The next important step is to make a backup. It’s always a good idea to make sure you back up your Mac before you do anything like this, just in case something goes wrong. We show you how to create a backup of your Mac here . We also have this guide on how to use Time Machine, Apple’s backup software.
• Be prepared to erase everything: If you’re using an older version of macOS when you partition your Mac, you’ll need to completely erase it! If you want to keep your current work, you’ll need to create a backup of your Mac and make sure it will fit on your smaller partitioned drive. Luckily, you don’t have to erase anything if you’re just creating a volume.
• There are alternatives: If erasing your Mac seems too complicated, you can try installing the alternative version of macOS on an external hard drive. We explain how to do it here: How to Run macOS from an External Hard Drive.
• Make sure you can run the versions of macOS you want:You won’t be able to run a version of macOS on a Mac that doesn’t support it, find out which version of macOS your Mac is compatible with.

How to Add a Volume to Your Mac

So you want to run two versions of the macOS operating system on your Mac. Your method will depend on which version of macOS you’re already using. If you have a modern Mac, this is a fairly straightforward affair. Even older Macs running High Sierra on an SSD, or with any version since macOS Big Sur installed, this process is straightforward because your Mac will use the Apple APFS file system.

APFS replaced the old file system: HFS+. APFS has many advantages, the main one being space sharing, which allows you to share the available space between different volumes on your disk. This way, more space can be made available at any time, rather than being allocated to the volume when it is created, as is the case with a partition.

So, if you are using APFS, you can create an APFS volume as we will show you below, and then simply install the new version of the operating system on that volume. You will not need to reformat anything. It couldn’t be simpler.

If you have an older Mac and are using an older version of macOS, or even Mac OS X, this is a bit more complicated because it requires a partition. You can find more information on how to do this towards the bottom of this article.

How to Create an APFS Volume

1. Back up your Mac in case things go wrong.
2. Open Disk Utility (you can find it in the Utilities folder in Applications, or just press Command+Space and start typing Disk Utility).
3. Click the drop-down menu next to the View button in the toolbar and choose Show All Devices. This will allow you to see the volumes on your disk. You probably have one called Home or Macintosh HD.
4. Select the Home (or Untitled) volume and click the + button to create a new volume. We have a more detailed guide on this process, which we recommend reading if you run into any problems here: How to Partition a Mac Hard Drive or SSD, or Create an APFS Volume.
5. You will need to give your volume a name, Beta would be a good idea if this is the beta version you are installing.
6. You can set the storage limit if you want (but it’s not required). To set a size limit, click Size options and enter the Reserve (minimum) and Quota (maximum) options. In the past, we’ve set the limit to 25GB. This number can be changed, but it’s not a simple process, so we don’t recommend setting a limit.
7. Now click Add to add your new volume to the Mac.

Now that you have your second volume up and running, you’re ready to install the macOS beta or an alternative version of macOS to the one you’re using. We’ll cover how to do that below.

If you’re using an older version of the Mac operating system and don’t have APFS, you’ll have a slightly more complicated path that requires a partition (more information at the bottom of this article).

How to Install Two Versions of macOS on One Mac

After creating your second volume using the guide above, you will be ready to install your second version of macOS.

1. Download the installer for your desired operating system. You can get the installer through Software Update or the Mac App Store. (See How to update macOS for details on how to get the installer.) Note: It will need to be a newer version than the one you’re currently using. If it’s not, the process will be more complicated, and you should read this: How to downgrade to an older version of macOS . Download it, but don’t start installing it yet.
2. Run the installer, but make sure to select the new volume you created and install the alternate macOS on that, not your main volume.
3. Now wait for your Mac to install the new operating system on the new volume.
4. When finished, your Mac will open in the volume with the new operating system installed.
5. When you’re ready to revert to your old version of the operating system, simply shut down your Mac and, while it’s booting up, hold down the Alt/Option key until you see the option to open from your original volume. This will allow you to choose which volume you want to use and which version of macOS you want to run.
6. When your Mac starts up, it will appear that you need to choose a network and enter the password. This is probably not the case, but in our experience, you can skip this step.

Apple (modified)

Apple (modified)

Apple (modified)

How to install macOS beta on a separate volume

The process is similar if you want to install a beta version of macOS on the second volume.

If you are setting up this release for the first time, you will need to sign up for the beta and download the macOS beta software. Once downloaded, you will need to install it on the new volume you just created, as per the instructions above.

We have a detailed explanation on how to sign up for the macOS beta and how to get the macOS beta.

We also have tips on downloading older versions of macOS here. For operating system options other than macOS, you can read our guides on how to install Windows on a Mac and how to install Linux on a Mac.

How to install a second macOS on a partition

If you need to create a partition because you have an old Mac, you will need to erase your Mac first. So, as we said above, make sure to make a backup.

The easiest way to create your score is to do the following:

1. Start macOS in Recovery Mode (start your Mac and hold down the Command and R keys until you see an Apple logo or a spinning globe).
2. Once in recovery mode, use Disk Utility to erase the primary hard drive and divide it into two partitions.
3. Now recover your Time Machine backup to this partition. Keep in mind that you won’t be able to recover a backup based on a newer version of macOS than the one you want to use on this partition.
4. You can also use the Install option in Recovery to install the version of macOS you want to run on the primary partition.
5. Now it’s time to install the other version of macOS in partition 2. Follow the steps here to install a second version of macOS, or the beta version of the new version of macOS, on the second partition.