Every new release of macOS comes with its share of undetected bugs, but most early adopters will tell you that Catalina has had more than most.

Catalina
One way of avoiding a disastrous upgrade to Apple's latest version of macOS is to partition your Mac's hard drive and install Catalina alongside your current operating system. That way, you can test out the apps that are most crucial to your daily workflow without risking your system's existing setup, not to mention your personal data.

Of course, it's not just Catalina that you can install on a separate partition – the associated steps below can be used to run any operating system alongside macOS. Keep reading to learn how it works.

What is a Disk Partition?

Partitioning your Mac divides the available hard drive space into individual sections, each of which acts as a separate volume that you can use to run two separate operating systems on the same computer. It's the same procedure that Apple's Boot Camp Assistant runs to let you install Windows alongside macOS, but whereas that creates the partition for you, here we're going to show you how to partition your drive manually.

But before you install macOS Catalina on a separate partition, it's worth familiarizing yourself with the way Apple's new file system works.

Catalina's File System Explained

Catalina is the first version of macOS to adopt wholesale the relatively new Apple File System (APFS), which is optimized for the flash storage used in recent Macs. Aside from introducing a bunch of other new technical features, an APFS-formatted partition uses a space-sharing "container" that can house multiple secure "volumes" or file systems. This allows the partition's free space to be shared on demand and allocated to any of the individual volumes in the container as required.

Catalina is installed on a dedicated read-only system volume, while your files and data are stored separately in another volume labelled with the suffix "- Data." The idea behind this setup is that it helps prevent the accidental overwriting of critical operating system files, since the user can no longer alter data or store files on the read-only system volume. In practice, the average user shouldn't notice any difference after the split, since both volumes appear in Finder as a single unified volume.

Remember to Back Up First

Before following these steps, ensure you have made a full backup of your system, which should be par for the course when making structural changes to your Mac's system drive. MacRumors cannot be held responsible for any data loss.

How to Create a New Partition on Your Mac

  1. Open a Finder window on your Mac and open the Applications folder.
  2. Scroll down and open the Utilities folder.
  3. Launch Disk Utility.
    applications

  4. Select your hard drive from the sidebar in the Disk Utility window (it's usually called "Macintosh HD"), and then look at the blue bar to check that you have enough space to create a new partition – around 50GB should suffice, but the more the better.
    disk utility

  5. Click the Partition tab.
  6. Click the plus (+) button below the pie chart.
    disk utility partition device

  7. In the Name: field, type a name for your new partition.
  8. In the Format: field, use the dropdown to select a Format for the new partition. If you're running macOS High Sierra, choose APFS. If you are running macOS Sierra or earlier, choose Mac OS Extended – Catalina will convert it to APFS automatically during the installation process.
  9. In the Size: field, enter the size in gigabytes that you'd like your new partition to be. Alternatively, using the ball on the edge of the pie chart, drag the radial line to adjust the size of the new partition.
    partition

  10. Click Apply.
  11. Check the summary of proposed actions, then click Partition to confirm.

If everything goes well, Disk Utility will create the partition in just a few minutes. When the boot volume is resizing, your Mac's screen may freeze for a while. This is expected behavior – whatever you do, do not power off your computer while the resizing takes place.

How to Download Catalina

The method for installing Catalina on your new partition will depend on the version of macOS you're currently using. If you're running macOS 10.14 Mojave, you can download Catalina via Software Update. If you're running macOS 10.13 High Sierra or an older version you will need to download Catalina from the Mac App Store.

Download Catalina via Software Update

  1. Launch System Preferences from your Mac's Dock, from the Applications folder, or from the Apple menu bar ( -> System Preferences...).
  2. Click Software Update.
    system prefs

  3. Your Mac will check for updates and show that macOS 10.15 Catalina is available. Click Update Now to download the installer.
    software update macos

Be prepared to wait while the installer downloads. It can sometimes take several hours, but you can continue to use your Mac while it continues to download in the background.

Download Catalina via the Mac App Store

  1. Launch the Mac App Store from the Applications folder.
  2. Search for macOS, or go straight to the Catalina download page.
  3. Click Get.
    Mac app store

  4. Enter your Apple ID and password if prompted.

Be prepared to wait while the installer downloads. It can sometimes take several hours, but you can continue to use your Mac while it continues to download in the background.

How to Install Catalina on Your New Partition

Once the Catalina installer has downloaded, it should launch automatically. After accepting the T&Cs, be sure to select the new partition on which you want to install Catalina.

Catalina
Follow any other onscreen instructions and allow the installer to restart your Mac and complete the installation.

How to Switch Between Partitions

If you're already booted into macOS, you can reboot from another drive or partition by following these steps.

  1. Launch System Preferences from your Mac's Dock, from the Applications folder, or from the Apple menu bar ( -> System Preferences...).
  2. Click Startup Disk.
    system prefs

  3. Click the lock icon in the bottom-left corner of the window to allow you to make changes.
  4. Enter your system admin password, then click OK.
  5. Select the partition drive you want to boot from on restart.
  6. Click Restart....

When powering on your Mac from scratch, hold the Option key when you hear the startup chime. This will activate the Startup Manager, where you can select which partition to boot from.

Related Forum: macOS Catalina

Popular Stories

Apple Vision Pro 2 Feature 2

Apple Reportedly Suspends Work on Vision Pro 2

Tuesday June 18, 2024 8:17 am PDT by
Apple has suspended work on the second-generation Vision Pro headset to singularly focus on a cheaper model, The Information reports. Apple was widely believed to have plans to divide its Vision product line into two models, with one "Pro" model and one lower-cost standard model. The company is said to have been deprioritizing the next Vision Pro headset over the past year, gradually...
apple watch series 9 display

Kuo: Apple Watch Series 10 to Get Larger Screen and Thinner Design

Monday June 17, 2024 1:20 am PDT by
This year's Apple Watch Series 10 will be thinner and come in larger screen sizes than previous models, according to Apple analyst Ming-Chi Kuo. In his latest industry note -10-and-98075c44ce92">shared on Medium, Kuo said the screen size options on the next-generation Apple Watch will increase from 41mm to 45mm, and from 45mm to 49mm, while being encased in a thinner design. For reference,...
2022 back to school apple feature

Apple's 2024 Back to School Sale Launching This Week

Monday June 17, 2024 12:27 pm PDT by
Apple will launch its annual Back to School promotion for university students in the United States and Canada this week, according to Bloomberg's Mark Gurman. Apple's back to school sales provide students with a free Apple gift card when purchasing a Mac or an iPad, and this year's promotion could help Apple push the new M2 iPad Air and M4 iPad Pro models. Last year, Apple offered U.S....
Apple Pay Later feature 1

Apple Discontinuing Apple Pay Later

Monday June 17, 2024 11:44 am PDT by
Apple is discontinuing Apple Pay Later, the buy now, pay later feature that it just launched last October. Apple Pay Later is being discontinued as of today, but people who have existing Apple Pay Later loans will be able to continue to pay them off and manage them through the Wallet app. Apple announced plans to end the feature in a statement provided to 9to5Mac, which also notes that...
iOS 18 CarPlay Feature

iOS 18 Adds These 5 New Features to CarPlay

Thursday June 13, 2024 7:44 am PDT by
Apple did not mention CarPlay during its WWDC keynote this week, but iOS 18 includes a handful of new features for the in-car software. Overall, there is not a whole lot new for CarPlay on iOS 18, with changes seemingly limited to the Messages and Settings apps so far. Below, we recap everything new for CarPlay on iOS 18. New for CarPlay on iOS 18 1. Contact Photos in Messages App...
iPod Nano vs iPod Pro Ad Feature 1

Apple Developing Thinner MacBook Pro, Apple Watch, and iPhone

Monday June 17, 2024 2:22 am PDT by
Apple intends to slim down the MacBook Pro, Apple Watch, and iPhone, with the new ultra-thin M4 iPad Pro a sign of the company's new design trajectory, according to Bloomberg's Mark Gurman. When the M4 iPad Pro was unveiled last month, Apple touted it as the company's thinnest product ever, and even compared it to the 2012 iPod nano to emphasize its slim dimensions. Writing in the latest ...
watchOS 11 Thumb 2 1

watchOS 11 Supports Automatic Nap Detection

Monday June 17, 2024 4:05 pm PDT by
watchOS 11 appears to include a new feature that allows an Apple Watch to automatically detect and record when you're taking a nap. As shared on Reddit, an Apple Watch owner took a nap and was able to see the sleep data recorded in the Health app, despite not putting the device in Sleep Mode. Right now, the Apple Watch only tracks and records sleep when it is in Sleep Mode, and there is no...