Apple makes it easy to update Macs to the latest version of macOS. Best of all, these updates are free. The latest version of macOS, Big Sur, is one of the most feature-rich releases on record and offers a good mix of new and updated tools. Despite this, there are a few reasons why you might have no choice but to revert to a previous version of macOS. For example, you may find that one of your most essential apps doesn’t work with Big Sur, or maybe your job requires testing apps on previous versions.
Whatever the reason, it’s possible to downgrade your Mac to a previous version of macOS, although it’s not as straightforward as the upgrade process.
Before you start
Apple releases a new version of macOS in September, October, or November of each year. Historically, this version was first revealed at the Worldwide Developers Conference (WWDC) in June. Until official release, the version is tested through a software testing process that sees regular beta releases released to developers and users of Apple’s public beta software program.
Despite months of testing, no version of the operating system is completely bug-free. It also takes time for external application developers to make the necessary changes to fully support the new version. These are two reasons why some people like to delay upgrading their machines until a bug fix (or two) is released.
Ordinary Mac users have little reason to revert to previous versions of macOS. Apple knows this, and that’s probably the main reason why downgrading is such a long process.
Therefore, you must take a deep breath and pause before taking these steps. For most people, this is not necessary at all.
Back up your files
If you’ve decided to downgrade, be sure to back up your Mac’s files. Ideally, you should already regularly back up your computer through Time Machine or some other solution. Before moving forward, make a final backup copy. This copy probably won’t be used, but it’s good to have in case something goes wrong while downgrading.
Decide how to downgrade
There are two ways to downgrade your Mac to a previous version. You can restore through Time Machine or install macOS from a USB drive.
Taking the Time Machine route is the easiest, although it does assume that you had a Time Machine backup of your system that predated you installed macOS Big Sur. Otherwise, a downgrade using Time Machine is not an option.
Third-party solutions like Carbon Copy Cloner work pretty much the same. But again, you need a copy of your files taken before updating to macOS Big Sur for this to work.
Using an external USB stick or other type of drive to downgrade is the best choice when you don’t have backup files. In this case, you will start from scratch with a fresh copy of macOS.
Downgrade using Time Machine
To use Time Machine and downgrade your Mac to a different version of macOS, follow these steps. This process involves the use of the ‘Command’ + ‘R’ command, which works differently on Intel machines than those with Apple silicone. And yet, Apple Silicone does not support versions of macOS prior to Big Sur, so the difference is irrelevant here.
To downgrade macOS through Time Machine, plug your Time Machine backup drive into your Mac, then restart the computer. As soon as the screen goes dark, hold down the ‘Command’ + ‘R’ keys until you see the Apple logo. Then choose the option “Restore from Time Machine backup” and click “Continue”. You will need to click “Continue” once more.
Then choose your “Restore Source”, which will be the name of your external device. From the list, choose the last backup made in a previous version of macOS. In this case, that would be the final version of macOS Catalina.
After the restore process is complete, you can use Time Machine backup to restore individual files if needed. However, this is a manual process.
Rollback using a bootstrap installer
You first need to create a bootable installer for a downgraded version of macOS. Once you have done that, you can install this version on your computer. As a reminder, you cannot downgrade Macs using Apple silicon.
To do this, connect the bootable installer to your Mac. Then go to the Apple menu and select System Preferences> Startup Disk. Choose the external drive as the startup disk, then click “Restart”. Make sure your computer is connected to a Wi-Fi connection.
After the Mac restarts, select “ Reinstall macOS ” in Utilities. Choose “Continue”. After this process is complete, your Mac has been downgraded to a previous version of macOS. Use Time Machine to restore previous files, if possible.