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Revert from Catalina to Original OS (Yosemite) or can I just revert to Mojave

iMac was recently updated to Catalina, and a piece of software that is used frequently does not work with Catalina, so we want to revert back from Catalina. The computer's original OS was Yosemite and may have been updated to El Capitan, but not further. We'd like to use a later OS, but just not Catalina. Is it possible to revert back to Mojave from Catalina, or does the computer have to be reverted back to the original OS and then updated to Mojave? The computer has been being backed up with Time Machine, but we could not restore from that because of an issue with file formats. So, now trying to figure out what we should do. Thanks.

Posted on Jul 13, 2020 11:59 AM

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Posted on Jul 13, 2020 2:29 PM

In the Recovery mode you use Disk Utility to erase the hard drive, then select Restore From Time Machine Backup.



Just make sure you pick the backup that was made prior to your upgrading to Catalina.

10 replies

Jul 13, 2020 12:06 PM in response to Barbara Batchelder

If you cannot restore using Time Machine then you will have to continue with Catalina or you will have to start over and using Internet recovery to restore Yosemite which will mean you lose data and apps. Have you considered updating or replacing the 32 bit app you cannot use in Catalina?


Also, did you try the instructions in https://support.apple.com/guide/mac-help/revert-to-a-previous-macos-version-mh15216/mac

Jul 13, 2020 12:24 PM in response to rkaufmann87

Thanks for your quick response. The company says they are working on an update to the program, but has been saying that for most of a year now (since Catalina was released). Catalina has only been installed a few days and really nothing has been done on the computer since other than email which is recoverable due to IMAP account. I have already read that support document you linked to and followed the instructions to try and restore from Time Machine. However, I get an error that says "This system can't be restored onto this disk because HFS systems can't be restored to space sharing APFS volumes. Reinstall macOS on this disk and then use Migration Assistant to transfer data from your backup instead." I guess we just need to revert back to original OS and then could update to Mojave.


Jul 13, 2020 1:55 PM in response to Old Toad

I got this error message when trying to restore from the last time machine backup prior to Catalina being installed. "This system can't be restored onto this disk because HFS systems can't be restored to space sharing APFS volumes. Reinstall macOS on this disk and then use Migration Assistant to transfer data from your backup instead."

Jul 13, 2020 2:08 PM in response to Old Toad

I did try booting into recovery mode using the Shift+Option+Command+R which is supposed to let you restore using the original OS which would have been Yosemite. However, when trying to do that, it did not show the Macintosh HD as an option to restore to. The only disk that showed was the external drive which is the Time Machine.


So, once into Recovery mode, do I then go into Disk Utility to do the erase? I assume I then have to get an OS installed before I can use migration assistant to restore files/apps from Time Machine? Or can I just do a restore from Time Machine once the erase is done? Would that get back the OS that had been running before Catalina was installed as well as all the apps/files?


Revert from Catalina to Original OS (Yosemite) or can I just revert to Mojave

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