Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

California

macrumors 68040
Original poster
Aug 21, 2004
3,885
90
I bought a 2018 Mac Mini in 2021 which I believe shipped with Big Sur. I just found out that I cannot downgrade to Mojave or even boot off an external drive with Mojave?

What is the workaround here? This is the i7 machine with 32 gigs of ram.
 

now i see it

macrumors G4
Jan 2, 2002
10,903
23,100
No mac has ever been able to run an OS older than the one that it shipped with. It’s always been impossible.
 

CoastalOR

macrumors 68040
Jan 19, 2015
3,025
1,147
Oregon, USA
The 2018 Mini has a T2 security chip, which the delivered configuration defaults to not allowing booting from an external media. Have you used the Startup Security Utility to allow booting from an external drive?

I bought a 2020 (2018) Mini in 2020 which came with Catalina installed. I used the Startup Security Utility to "Allow booting from external or removable media" and I was able to boot from a bootable drive with Mojave macOS.

 
Last edited:

DeltaMac

macrumors G5
Jul 30, 2003
13,589
4,483
Delaware
No mac has ever been able to run an OS older than the one that it shipped with. It’s always been impossible.
That is incorrect in certain situations. "... always been impossible' is a little restrictive, don't you think?
Example: my 2017 MBAir shipped originally with Sierra, but shares the same logic board with the 2015 MBAir, which shipped with Yosemite (OS X 10.10). Even though I have been running Monterey, it will boot to an external Yosemite system, if I need to do that (keeping in mind that it shipped with Sierra, 2 generations newer.)
I would change your statement to read something like:
Macs usually cannot boot to an OS older than the OS that model originally was released with. There are a few limited exceptions to that, but generally cannot be done.
 

California

macrumors 68040
Original poster
Aug 21, 2004
3,885
90
The 2018 Mini has a T2 security chip, which the delivered configuration defaults to not allowing booting from an external media. Have you used the Startup Security Utility to allow booting from an external drive?

I bought a 2020 (2018) Mini in 2020 which came with Catalina installed. I used the Startup Security Utility to "Allow booting from external or removable media" and I was able to boot from a bootable drive with Mojave macOS.

I'm going to try this now. My machine is 2018 but manufactured in 2021, and I think shipped with Big Sur.
 
Last edited:
  • Like
Reactions: MBAir2010

California

macrumors 68040
Original poster
Aug 21, 2004
3,885
90
No mac has ever been able to run an OS older than the one that it shipped with. It’s always been impossible.
? Nope, this is absolutely incorrect. Macs have always been able to use the OS that it ORIGINALLY shipped with at launch of the machine. The 2018 Mac Mini shipped with Mojave in 2018, and this is the precise reason I purchased it three years later..

PS the 13" 2012 MacBook Pro was manufactured by Apple for four straight years (just like the 2018 Mac Mini). I believe it shipped originally with Mavericks. So even if you bought it new in 2016 and it had High Sierra on it or Mojave, you could still ALWAYS run Mavericks on it.

This was part of my strategy in purchasing the Mac MIni... so I could run older and newer software.
 

DeltaMac

macrumors G5
Jul 30, 2003
13,589
4,483
Delaware
...
PS the 13" 2012 MacBook Pro was manufactured by Apple for four straight years (just like the 2018 Mac Mini). I believe it shipped originally with Mavericks. So even if you bought it new in 2016 and it had High Sierra on it or Mojave, you could still ALWAYS run Mavericks on it.

This was part of my strategy in purchasing the Mac MIni... so I could run older and newer software.
You are off a little on that... That 2012 MBPro was introduced in June 2012, before Mountain Lion was released, so shipped first with Lion installed, 2 generations before Mavericks - even older than you said!
 

Fishrrman

macrumors Penryn
Feb 20, 2009
28,732
12,844
I'm going against the grain here.

I contend that the OP's 2018 Mini SHOULD be able to run Mojave, even if it shipped in 2020 with Big Sur on it.

To enable this, the OP will have to:
1. Get a copy of Mojave (easy)**
2. Get a USB flash drive 16gb. Format it to "Mac OS extended, journaling enabled, GUID partition format".
3. Create a bootable USB flashdrive (I recommend using either "DiskMaker X" or "Install Disk Creator" for this job)
4. Boot from the flashdrive
5. COMPLETELY ERASE the Mini's internal SSD
open disk utility and you MUST go to the "view" menu and choose "show all devices".
Then, the "top line on the left" is the physical drive -- THIS is what you need to erase.
6. Install Mojave
7. Restore from a backup (although I'm unsure whether setup assistant will migrate from a backup created with Big Sur, or not).

The 2018 Mini's originally shipped with Mojave, and even subsequent firmware updates should not prevent one from booting or running Mojave.

If that were true, then I couldn't still be using Mojave with MY 2018 Mini, since I've installed Ventura on an external drive, and can boot and run the Mini with that, too.

The firmware updates (to Ventura) did NOTHING to prevent booting/running from Mojave.

** If you're having trouble getting Mojave, go here:
Download the Mojave patcher utility.
(we're not going to patch anything, we just need this to get Mojave)
Launch the utility. Dismiss the alert if it pops up.
Go to the "tools" menu and choose "Download Mac Os Mojave"
Once it's downloaded, that's it, you can quit the utility.
Now you have the Mojave installer.
 
Last edited:

DeltaMac

macrumors G5
Jul 30, 2003
13,589
4,483
Delaware
Just a reminder - the Startup Security utility on that 2018 mini needs to be set so the OP can boot from external drives.
 

California

macrumors 68040
Original poster
Aug 21, 2004
3,885
90
I'm going against the grain here.

I contend that the OP's 2018 Mini SHOULD be able to run Mojave, even if it shipped in 2020 with Big Sur on it.

To enable this, the OP will have to:
1. Get a copy of Mojave (easy)
2. Get a USB flash drive 16gb
3. Create a bootable USB flashdrive (I recommend using either "DiskMaker X" or "Install Disk Creator" for this job)
4. Boot from the flashdrive
5. COMPLETELY ERASE the Mini's internal SSD
6. Install Mojave
7. Restore from a backup (although I'm unsure whether setup assistant will migrate from a backup created with Big Sur, or not).

The 2018 Mini's originally shipped with Mojave, and even subsequent firmware updates should not prevent one from booting or running Mojave.

If that were true, then I couldn't still be using Mojave with MY 2018 Mini, since I've installed Ventura on an external drive, and can boot and run the Mini with that, too.

The firmware updates (to Ventura) did NOTHING to prevent booting/running from Mojave.
I'll try this with Diskmaker instead of downloading Apple's bootable installer. I don't need the Big Sur data. It is blocking me from chosing Mojave as a start up drive. Apple is saying I cannot do this, either because of the date I purchsed the machine in late 2021. The machine was not cheap and it's a brick to me now because I'm not ready for latest OS in my workflow.
 

Fishrrman

macrumors Penryn
Feb 20, 2009
28,732
12,844
OP:

This isn't going to work unless you boot from a bootable USB flashdrive.

And... again... you have to COMPLETELY ERASE the internal drive.

Pay attention to EVERY step in my instructions above.
I have added a couple more steps.

Also, if DiskMaker X stumbles, try Install Disk Creator. Sometimes when one won't work, the other one WILL...
 
Last edited:
  • Like
Reactions: MBAir2010

DeltaMac

macrumors G5
Jul 30, 2003
13,589
4,483
Delaware
How did you make your "Mojave USB" bootable? If you simply copied the installer app to a USB drive, that won't work, and would explain why the mini won't recognize the USB drive (It's not yet bootable)
 

California

macrumors 68040
Original poster
Aug 21, 2004
3,885
90
OP:

This isn't going to work unless you boot from a bootable USB flashdrive.

And... again... you have to COMPLETELY ERASE the internal drive.

Pay attention to EVERY step in my instructions above.
I have added a couple more steps.

Also, if DiskMaker X stumbles, try Install Disk Creator. Sometimes when one won't work, the other one WILL...
Ok TY will let you know (thank you again)
 

California

macrumors 68040
Original poster
Aug 21, 2004
3,885
90
I'm going against the grain here.

I contend that the OP's 2018 Mini SHOULD be able to run Mojave, even if it shipped in 2020 with Big Sur on it.

To enable this, the OP will have to:
1. Get a copy of Mojave (easy)**
2. Get a USB flash drive 16gb. Format it to "Mac OS extended, journaling enabled, GUID partition format".
3. Create a bootable USB flashdrive (I recommend using either "DiskMaker X" or "Install Disk Creator" for this job)
4. Boot from the flashdrive
5. COMPLETELY ERASE the Mini's internal SSD
open disk utility and you MUST go to the "view" menu and choose "show all devices".
Then, the "top line on the left" is the physical drive -- THIS is what you need to erase.
6. Install Mojave
7. Restore from a backup (although I'm unsure whether setup assistant will migrate from a backup created with Big Sur, or not).

The 2018 Mini's originally shipped with Mojave, and even subsequent firmware updates should not prevent one from booting or running Mojave.

If that were true, then I couldn't still be using Mojave with MY 2018 Mini, since I've installed Ventura on an external drive, and can boot and run the Mini with that, too.

The firmware updates (to Ventura) did NOTHING to prevent booting/running from Mojave.

** If you're having trouble getting Mojave, go here:
Download the Mojave patcher utility.
(we're not going to patch anything, we just need this to get Mojave)
Launch the utility. Dismiss the alert if it pops up.
Go to the "tools" menu and choose "Download Mac Os Mojave"
Once it's downloaded, that's it, you can quit the utility.
Now you have the Mojave installer.
OMG, I THINK IT WORKED. I booted from a Mojave ext drive, not installer and... importantly, ignored Network connectivity/wifi this time. Booted from external Mojave drive and now erased mac mini main drive. THANK YOU FOR hanging in there and reminding me to follow instructions. In four hours on phone with apple, they could not help. TY so much
 
  • Like
Reactions: Fishrrman

Fishrrman

macrumors Penryn
Feb 20, 2009
28,732
12,844
OP:
"In four hours on phone with apple, they could not help."

<--- Solves the problems that Apple can't... :cool:
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.