Desperately need to remove Catalina and reinstall Mojave

I had the same problem and found the solution. A program I use did not work on Catalina after I upgraded from High Sierra. Luckily I had a time machine backup from high sierra although when trying to restore from the Time Machine it gave me the error message. To overcome this I had to go on disk utility and delete both Macintosh and mackintosh HD by using the minus button then the volume reappeared as SSD flash storage I then raised the volume renaming at Macintosh using OS extended (journaled) Then I went back to restore from Time Machine and everything worked out as planned. I hope this helps I’m sure it works the same for operating systems other than High Sierra.

Thank you SO much @Scily98 I followed your procedure to the letter and it worked for me even when reverting back to El Capitan! My only note (for novices like me) is with the step “raised the volume” this means you click on the new SSD flash volume on the left, then choose “erase”, then rename Macintosh HD with OS Extended journaled, I kept the next box below that as the default. Thanks again you’ve totally saved my bacon!!!!

Ditto on the not a stupid question I am not a computer-minded person, I spent two full days in front of my computer trying to reverse this upgrade without erasing my hard drive since I couldn't trust the backup process I had been using. I was having the same issues with Catalina; heating my machine/fan being constantly on when nothing's open, everything slower, rainbow wheels, had to find a tedious workaround through Terminal to open Photoshop, etc. I came to a lot of dead ends and the thing that worked ended up being super easy, once I manually backed up everything onto a different external drive (in case this process didn't work either). When you're in the disk utility in Restore mode above the listed hard drives is a "View" drop down menu, and I clicked view all, then selected the drive at the very top (my options were Apple SSD Sm25-something-or-another and below that Macintosh HD) and clicked "Erase" I renamed the drive the same thing it was named before, and on the drop down menu below that selected OS Extended Journal. Now I was having trouble with my Time Machine backup because my hard drive was set to the APFS or whatever, and my external drive was set to OS Extended Journal and they are not compatible, meaning my Time Machine backups were useless. By erasing my hard drive and setting it to OS Extended Journal it made my hard drive compatible with my external drive so I was able to hit the "Restore From Time Machine Backup" option in Restore Mode and what do ya know, I'm back in El Capitan and everything is purring. Honestly I'm not sure if I explained the why correctly but I can say that what I did worked. Hope this helps

Revert your Mac to a previous macOS version - Apple Support

Thanks so much for helping us all out with this issues. I've joined the band of idiots making bad decisions 2 days ago, and now I need to go back to downgrade from Catalina as some of the softwares I used for work are not compatible.

I've read everyone's posts and tried to put together all the steps and tips. But before I embark on this quest, I'd like to triple check that I got this right:

• First of all, I have a Time Machine Backup pre-Catalina on an external hard drive, and also a new backup made from Catalina which exlcludes the Apps and the System folders, just in case
• Then I have created the bootable installer onto an external device (in my case I'm using the same external hard drive where my back up is, which I have partitioned and formatted so it's a Mac OS Extended Journal format).
• At this point, I need to restart the machine in recovery mode
• Open Disk Utility
• Erase Macintosh HD and Macintosh HD - Data after changing their format to Mac OS Extended Journal by clicking on "-"
• Then select the new installer and click '+' to rename it as Macintosh HD
• Go back to restore from Time Machine

I hope I got the process right. Please let me know if I made any mistakes, and I apologise for the poor terminology.

I'm trying to go back to El Capitan from Catalina, I've followed the thread and done as instructed, but now my mac won't turn on it gets to image below.. :(

is it anything to do with the apple disk image? do I need to delete this too? any advice will be useful!

So, I tried yesterday but I was faced with slightly different options and I didn't feel like testing my luck (or capabilities in this case).

In my Utility Disk I cannot change the Macintosh HD and Macintosh HD Data's format to Mac OS Extended Journal. However, I could do it with the "container disk" they're both in. This container disk is itself inside the Fusion Drive.

At this point I'm unsure about which one I should erase and rename. And if I erase the "Container disk", should I rename it as "Macintosh HD" or keep "container disk"?

Apologies, I'm terrified I'm going to make a fatal mistake..

I tried these steps, and my Mac completely useless. It failed to boot.

I was desperate with catalina flaws then I seek for help to get back using my TM. Then I found this discussion. I'm sure I have follow all the step given, then my mac successful back to El Capitan. But after I restart my mac, the bar loads until 3/4 then it fade out, blink again at the apple and 3/4 bars and then fade out again and again, and again.

Please, I have followed your steps, then you have to help me to solve this 🙏

You can revert but, only of you have a backup prior to the install. I ran foul of this problem created by Apple Inc. Eventually had to revert to a very old full backup as Catalina seems to block partial restores from previous OS versions. Good luck.

Not yet. I would love to be able to just go back to a backup from my external hard drive but at this point would settle for wiping everything and going back to a previous OS (preferably El Capitan, as that was the last OS I was running and everything worked beautifully). When I go into Restore mode though alas, I can only restore to Catalina.

So I followed apple’s instructions on making a bootable usb for El Capitan but now the only option in the startup disk utility is my hard drive. It apparently is not detecting the usb, even though disk utility and finder and everything else recognizes it.

Did you restart in Catalina and try to use disk utility in Catalina (that doesn't work)?

You need to open disk utility from the screen that you get when you try to restore: "On your Mac, choose Apple menu  > Restart. After your Mac restarts (some Mac computers play a startup sound), press and hold the Command and R keys until the Apple logo appears, then release the keys."

From this screen choose disk utility instead of "Restore from a Time Machine Backup."

yeah definitely tried that and it didn’t work. What did end up working though was on the restore screen erasing my hard drive and setting the new parameters to match the backup drive I used, once that was done I got to roll back to a time machine backup that had El Capitan and everything went back to working perfectly. Thanks everybody for the input!

Hi - I'm trying to do exactly what you did - revert to El Capitan from Catalina via Time Machine back up. I am getting stuck on the point where you delete the Macintosh and Macintosh HD and then rename an SSD that shows up? I have literally never done anything like this, but I knew I should be able to do a restore to a previous back up. This step is confusing and I want to make sure I understand. When you say to 'rename Macintosh HD with OS Extended journaled', can you explain what that means? What would the new name be? And if OS Extended is referring to something I need to use and it isn't the actual name - please direct me.

I'm sorry, I feel like this question must sound so stupid, but I am really not even at novice level. I am an idiot stuck with a bad decision - taking the chance to upgrade to Catalina when I shouldn't have. But truly thought I'd be 'ok' since I was supposed to be able to revert back to previous Time Machine back up. I've been now dealing with this for at least 9+ hours between yesterday and today. Hoping I don't have to stick with Catalina - it's awful, it's heating my machine when nothing is open, I've lost photos, I hate it. Any help - and as detailed as possible - would be so incredibly greatly appreciated!

Hello not a stupid question. The Disk should be named “Macintosh HD” and the OS Extended Journal is the format of the disk. Usually a drop down under where you rename the disk. I’m not totally sure you will be given a format option if you are in the restore from time machine section so you may not need to worry about it.