How to downgrade from Catalina OSX
You installed Apple’s new MacOS Catalina on your Mac, but you might be having issues with the new version.
Unfortunately, you can’t simply revert back to Mojave. The downgrade requires wiping your Mac’s primary drive and reinstalling MacOS Mojave using an external drive. If your Mac initially shipped with Mojave, however, you can skip the external drive instructions.
Step 1: Back up your Mac
Before anything, create a current Time Machine backup to save your files, or send everything to the cloud, whether it’s Dropbox, OneDrive, iCloud, and so on. Chances are you may already have a backup prior to installing Catalina. If not, do so now before moving on to the next step. As stated, downgrading to Mojave requires wiping your Mac’s drive.
If you need help backing up your Mac, follow these step-by-step instructions.
Step 2: Enable external media booting
This step applies to MacBook Pro, MacBook Air, and Mac mini models released in 2018 and newer. It also applies to the iMac Pro released in 2017 and newer. These devices include Apple’s T2 security chip providing secure boot, encrypted storage, live “Hey Siri” commands, and more.
To verify that you have this chip, follow this path:
Apple button > About This Mac > System Report > Controller (or iBridge)
If your Mac doesn’t include Apple’s T2 security chip, you won’t need to enable external media booting. Otherwise, restart the Mac and hold down the Command and R keys until the device boots into Recovery Mode.
With Recovery Mode open, click Utilities on the toolbar followed by Startup Security Utility in the drop-down menu. Enter the administrator credentials when prompted then check the box next to the Allow booting from external media option listed under External Boot.
Step 3: Download MacOS Mojave
You’ll need to grab MacOS Mojave from the Mac App Store. The best way to retrieve a copy is to follow this link on a Mac, as Mojave doesn’t show up when performing a search within the Mac App Store itself.
Clicking the link should automatically load Mojave’s product page within the Mac App Store app.
Step 4: Prepare your drive
To continue on, you’ll need to format an external drive. Connect an external drive and follow this path:
Finder > Applications > Utilities > Disk Utility
Select your drive listed under External and click the Erase tab. Name the drive, select the proper format (MacOS Extended or APFS), select GUID Partition Map if available, and then click Erase. Select Done when the formatting completes.
Now the external drive needs to be bootable. Follow this path:
Finder > Applications > Utilities > Terminal
Type the following into the Terminal. Remember to replace “YourExternalDriveName” with the drive’s actual name you created in the formatting step.
sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia –volume /Volumes/YourExternalDriveName
Press the Enter/Return key after typing the command. You’ll need to enter the administrator password when prompted followed by the “Y” key to confirm.
Step 5: Wipe your Mac’s drive
With MacOS Mojave now installed on an external drive, you’re ready to wipe your Mac’s drive. Don’t connect the drive just yet. Instead, restart and hold down the Command and R keys until the device boots into Recovery Mode.
Next, click the Disk Utility option followed by Continue. On the following screen, select your Mac’s primary drive and click the Erase button. Follow the instructions to pick a drive name, file format, and GUID Partition Map.
Step 6: Install Mojave
If your Mac shipped with MacOS Mojave, restart and hold down the Shift, Option, Command, and R keys simultaneously. This will automatically install Mojave from an image located on a dedicated partition.
Otherwise, connect your Mac to the internet, connect the external drive, and restart via the Apple icon in the top left corner. As the Mac restarts, hold down the Option key.
The following screen will present a list of startup disk options. Select your external drive containing the MacOS Mojave installer and click Continue.
Step 7: Use Time Machine
Now that MacOS Mojave is up and running, you want to use Time Machine to restore your settings and files to their pre-Catalina state.