How to Downgrade from Catalina to Mojave Using Time Machine
Time Machine is macOS’s built-in backup utility. And if you want to return to Mojave after you’ve upgraded, it can help you with that, too. If you realize soon after upgrading that you want to downgrade macOS, you can restore a backup from before the change. This technique has a time limit, unfortunately; you have to use it before the program dumps the old backup.
How to Downgrade from Catalina to Mojave with an Installer
If you don’t have a Time Machine backup with Mojave, you still have some options. The following process uses an attached disk or even a flash drive (assuming it’s a big enough flash drive) to be the drive you install Mojave from to your current system.
How to Downgrade from Catalina to Mojave by Restoring Your Computer
The above instructions work for most cases in which you’d go back to Mojave. But you may have another option available to you: If your computer shipped with Mojave pre-installed, you can restore it by skipping a lot of the above steps. If not, go to Step 11. Skip to Step 20. Here’s how to downgrade from Catalina to Mojave by restoring your computer.
