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Downgrade OS to Mojave

I've followed MacWorld's instructions on downgrading to Mojave from Catalina (because Catalina doesn't support my high-res scanner) by booting from a USB drive that contained "Install Mojave OS" and I expected that it would erase my HD and install Mojave. Instead it installed Mojave on a new "HD-Data" and Catalina and all my apps and data (pictures, movies, etc.) are still there. But it now boots from Mojave. What did I do incorrectly? Thanks!

MacBook Pro 13", macOS 10.14

Posted on Mar 27, 2020 9:29 AM

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Mar 27, 2020 9:42 AM in response to DowngradeOStoMojave

You did not wipe the drive as is required. How to Downgrade from macOS Catalina to Mojave or Earlier.


  1. Restart the computer. Immediately, at or before the chime, hold down the Command and R keys until the Apple logo and progress bar appear. Wait until the Utility Menu appears.
  2. Select Disk Utility from the Utility Menu and click on the Continue button.
  3. When Disk Utility loads select the target drive (out-dented entry w/type and size info) from the Device list.
  4. Click on the Erase button in Disk Utility's toolbar. A panel will drop down.
  5. Set the partition scheme to GUID.
  6. Set the Format type to APFS (SSDs only) or Mac OS Extended (Journaled.)
  7. Click on the Apply button, then wait for the Done button to activate and click on it.
  8. Quit Disk Utility.
  9. Insert your bootable USB flash drive and select Restart from the Apple menu.
  10. Immediately, at or before the chime, hold down the Option key until the Boot Manager screen appears.
  11. Select the icon of your bootable USB flash drive.
  12. Click on the arrow button under the drive icon.


Mar 27, 2020 9:36 AM in response to DowngradeOStoMojave

Did your MacBook Pro come with macOS Catalina originally? If so, then Apple does not provide a method to downgrade it to an earlier operating system. Since we don't know what MacWorld article you are referring to, would you post it please?


Finally, did you make either a clone copy or Time Machine backup of your notebook BEFORE to attempted to downgrade to Mojave?

Mar 27, 2020 11:11 AM in response to Tesserax

Thanks for the reply. My Pro came with Mavericks originally, and I upgraded as releases became available. Catalina killed my Epson high-res slide scanner driver, and I waited 3 months for them to release an update, which they didn't, so that's why I followed the instructions in the below MacWorld UK article: https://www.macworld.co.uk/how-to/mac-software/downgrade-macos-3581872/

I copied all data from my laptop to a USB drive

Mar 27, 2020 11:19 AM in response to Kappy

Thank you so much for your thorough reply. I will follow these instructions. I did first back up all data to a USB drive and synced all browsers so I should be able to recover everything and then use the Mojave driver for my Epson slide scanner, which I know worked before I upgraded to Catalina. By the way, the Macworld UK article whose instructions I followed is: https://www.macworld.co.uk/how-to/mac-software/downgrade-macos-3581872/ Note that this article does NOT precisely instruct on how to erase my current HD before installing Mojave - your reply does. Thanks again!

Downgrade OS to Mojave

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