Downgrading a Mac that shipped with Catalina to Mojave

Apple has started shipping Mac models that used to come with Mojave pre-installed with Catalina. If your organization has blockers for Catalina (incompatible software, etc.) you may want to install Mojave on these Macs. Unfortunately, this is not so easy.

Important Notice: these instructions will only work for Mac models that can boot to Mojave. Usually a Mac requires at least the version of macOS that the model shipped with when it was introduced. As of this writing, all new Macs require at least Mojave. The exceptions are the iMac Pro (High Sierra) and the MacBook Pro 16“ and the Mac Pro (2019) which both require Catalina. You cannot use these instructions to force a Mac Pro or MacBook Pro 16” to boot to Mojave. Any new Mac models that Apple introduces from now on, will also require Catalina and cannot be downgraded to Mojave.

(Not meant as a challenge. I am aware that someone might be able to hack together a Chimera Mojave with Catalina drivers. These ‘solutions’ are not supportable on scale.)

Directly downgrading from Catalina to Mojave with the startosinstall --eraseinstall command will fail. Attempts to run the Mojave installer from a Catalina Recovery (local or Internet) will also fail. The reason seems to be that the Mojave Installer application chokes on some aspect of Catalina APFS. Apple is likely not very motivated to fix this.

So far, the recommendation has been to boot to Internet Recovery with the shift-command-R key combination at boot. This used to boot to a Mojave (more specfically, the system the Mac shipped with) recovery system, and then you can wipe and re-install Mojave. However, if a Mac was shipped with Catalina pre-installed, it will boot to Catalina Internet Recovery, regardless of whether the Mac can boot to Mojave or not.

We have to get creative.

External USB Installer

The solution requires a Mojave Installer USB disk. First download the latest Mojave installer. You can do so from by following this App Store link. If you are running Catalina, you can also use the new option in softwareupdate:

> softwareupdate --fetch-full-installer --full-installer-version 10.14.6


Then you can use the createinstallmedia command in the Install macOS application to build an external Installer Drive on a USB drive. You probably want to add the --downloadassets option to add the current firmware to the USB drive as well.

> createinstallmedia --volume /Volumes/Untitled --downloadassets


This will delete the target volume data on the USB disk.

Enable External Boot

To boot a new Mac with a T2 chip off an external drive, you need to allow external boot from the Security Utility in the Recovery partition. This utility is protected and requires the password of a local administrator user to access. When you get a new Mac “out of the box,” you cannot directly boot to Recovery to change this.

Instead, you have to boot to the pre-installed Catalina, work your way through the Setup Assistant, and create a local administrator user before you can boot to Recovery to change this setting.

You also need to connect the Mac to a network with non-filtered/proxied access to Apple’s servers, either with Wifi or an ethernet adaptor. You can see which services and servers the network needs to be able to access in this kbase article. You will definitely need the servers listed under ‘Device Setup’ from that list and many of the others, depending on your deployment workflow.

This network connection is required to verify the integrity of the system on the USB Installer drive. You could also disable ‘Secure Boot’ entirely, but that is not recommended as it will, well, disable all system security verifications.

Now, reboot the Mac and hold the option key, from the list of devices to boot from, select the Mojave Installer drive. Once booted to the Mojave installation drive, start Disk Utility. In Disk Utility, erase the entire internal drive. You may have to choose ‘Show All Devices’ from the View menu to be able to select the internal drive with all sub volumes, not just the system or data volume.

Then you can quit Disk Utility and start the Mojave installation process.

After completing the installation, you want to remember to return to Recovery and re-disable external boot again. However, you need to create a new admin account on the disk before you can do that…

Avoiding the Downgrade

This is obviously tedious and really hard to automate. (I have been wondering if you could build a MDS workflow, but this one would require at least three reboots.)

The preferred solution is for IT departments and organizations to have the workflows and infrastructure in place to support and use “latest macOS” (Catalina). Apple is discouraging system downgrades or using anything but “latest macOS.” On newer hardware — like the MacBook Pro 16″, Mac Pro 2019, and every new Mac Apple will introduce from now on — downgrading to Mojave is not possible at all, so you have to support Catalina when you (or your users) get those Mac models.

As mentioned before, I do not believe there is much motivation at Apple to simplify this particular workflow. It serves Apple’s interest and vision to push the latest macOS over previous versions. From a user perspective it allows better integration with their iOS and other Apple devices. From a security standpoint it provides the latest security updates and patches. Apple provides security updates for the previous two macOS versions, but those notoriously do not fix all the vulnerability that the latest macOS gets.

However, in some cases you may have blocking applications that cannot run, or cannot be upgraded to run on Catalina. Then this workflow can be a ‘last ditch’ solution until you get those ‘blockers’ sorted out.

Maybe the best solution is to use this complex and work intensive downgrade workflow as leverage to push for “latest macOS” support in your organization.

Thanks to Robin Lauren and Mike Lynn for figuring this out on MacAdmins Slack and sharing their results.

64 thoughts on “Downgrading a Mac that shipped with Catalina to Mojave”

  1. Great article! I have a new 27″ iMac that came with Catalina. However, I need to run Mojave on it until I’m able to migrate from a couple 32 bit Apps. To do this, I plan on running Mojave by simply booting my new iMac from a SuperDuper backup I made of my old (Mojave) computer on an ext. SSD. Note, you can select the drive you normally wish to boot from in Preferences. Comments?

    1. I should have mentioned that in the post. The 2019 iMac models do _not_ have a T2 chip. They do not have external boot disabled by default (and cannot disable it, unless you set a firmware password). So you don’t have to jump through quite as many hoops to boot to Mojave as for the T2 Macs (all other currently sold Macs).

  2. I have tried to use Parallels to give me a Mojave version of the system on a newly purchased iMac Retina 2K, 2017. With no explanation I could not install the recently downloaded Install Mac OS Mojave. I have searched for an answer but no one has replied. I cannot find any discussion on the internet except for this article on issues with the use of Mojave on new macs. Is here any diagnostic I can run to confirm if my problem is what you have discussed in this report?

    1. if the Mac in question is on Catalina (no matter how it got there), you will need to boot off an external drive and wipe and install. Since the 2017 iMac does not have a T2, you at least don’t have to do the dance to enable external boot first.

      If the Mac is on an older version of macOS and you are having trouble running with the Mojave installer, you might have a version with an expired certificate:

      https://derflounder.wordpress.com/2019/10/16/certificate-used-to-sign-older-apple-software-expiring-on-october-24-2019/

      Make sure to download a brand new installer by following the link in this post: https://support.apple.com/en-us/HT210190

      Remote diagnosis is hard. I hope this helps.

      1. Make sure to download a brand new installer by following the link in this post: https://support.apple.com/en-us/HT210190
        ——————————
        Before I click “Get” from this link, I just want to verify that this will only download the installer, not actually try to install automatically like all the other “Get” buttons do. Thanks!

        1. It will download, install and open the Installer application, but not start the actual upgrade. You can quit out of the Installer application.

  3. You can also use DiskMaker X 8 for macOS Mojave.app to create an install disk (or disk image). Unfortunately, it won’t work in Mojave without a bit of a hassle (see the ReadMe file). DiskMaker 9 is available for Catalina, but it is not fully debugged yet. There is also a DiskMaker X Pro app available that can create 7 years of OS X bootable installers on a single disk. I haven’t tried it yet, but it sounds like a good idea—I’ll need a disk of at least 64 GB to do it. If the disk is larger than that, a separate partition is created for extra stuff.

    That said, I won’t be using Catalina until I absolutely have to. There are no must have features for me. And the loss of 32bit compatibility is a deal breaker. For example, if you are still using Adobe CS6 apps, most of them are 32bit. And they definitely won’t be upgraded. You’ll have to get on the Adobe Creative Cloud bandwagon, which is an expensive proposition. Just to use Catalina? I think not.

    Still, for those getting new Macs this downgrade solution may be essential. One should take care to buy a new Mac, like the iMacs, that are still Mojave compatible. If you can afford a Mac Pro, chances are you can afford all the new software you’ll need, so you won’t have to worry about downgrading. For the average Mac user, though, Catalina is certainly problematic.

  4. One thing I’ve found, if you’re using an MDM/DEP solution, is the Secure Token is not enabled on the administrator account, which will return an ~”admin not found” error in Startup Security Utility. But if you update the preboot via Terminal under the administrator account, it will then recognize it in Startup Security Utility.

    sudo diskutil apfs updatePreboot /

    Hope that helps anyone. It was a total pain at first for me.

  5. I bought a 2019 iMac with preinstalled Catalina. I needed Mojave because of a 32 bit program.

    I rebooted using ‘command R’ deleted the Macintosh HD. Tried to install Mojave. He didn’t take it.
    Tried to use a timemachine back-up from another iMac. He refused and stated it had to be the same type of iMac.
    Made a timemachine back up from another 2019 iMac running on Mojave. This worked out. Although I had to repeat to procedure.

    It looks like this helped me in successfully downgrading a 2019 iMac with preinstalled Catalina to Mojave

    1. Hi im in the exact situation. Unfortunately I dont have another 2019 imac running on mojave. I have a 2014 mac book pro and an old 2012 imac running on sierra. My hands are tied. Can I use the back up from those two computers to downgrade? Thanks

  6. Since you mentioned imac pro 2019 and mac book pro 2019 won’t work when it comes to downgrading to mojave, would my imac 2019 (21 inch retina) work for the downgrade? Thanks!

    1. There is no iMac Pro 2019. The Mac Pro and the MacBook Pro 16″ require Catalina. The 2019 iMac can be downgraded to Mojave and as I stated in a previous comment, since the iMac does not have a T2 chip you can just boot from an external drive without needing the above process to enable external boot.

  7. Macbook Pro 13 user here, bought at the end of last year and it shipped with Catalina. I’m trying to get Mojave to install and I’ve gone through all the steps to:
    1. create install USB disk for Mojave
    2. Boot from Mojave install disk
    3. Delete internal SSD
    4. Install Mac OS… here, it only gives me a choice to “Reinstall macOS” and goes out and tries to grab Catalina. It doesn’t use the install files on the USB to install Mojave!

    Any ideas?

  8. Hi.
    Great article.

    Is it possible to apply this solution to degrade an iMac 21.5 “Core i5 2.3Ghz | 8GB RAM | 1TB HDD originally released with Sierra in 2017 and currently sold by Apple with Catalina?

    My wish is to install High Sierra in this iMac 2017 that Apple now sells with Catalina.

    Thanks in advance.

    1. It should work. Since the iMac does not have a T2 Chip you don’t need the steps to enable external boot. Just create an external High Sierra installer drive and try!

      1. Thank you, Armin.
        The quality of this article and the endorsement of your response is the best point I have found so far.
        But I apologize for insisting that this iMac 2017 is being sold by Apple with Catalina installed.
        If I finally buy it and make this downgrade successfully I will communicate it right here.

        In any case thanks again.

  9. I have a 2019 Mac Book Pro 13”. I bought it refurbished and it was supposed to have a manufacture date of June 2019, which would mean it originally had Mojave since Catalina was released later in the year. After contacting Apple, the rep. told me my computer was actually manufactured on December, 2019 which means the original OS is Catalina. Is there any way to bypass this T2 chip in order to install Mojave?

  10. Hello,
    I picked up a Mac mini 2018 model with 64 gigs of RAM and all the upgrades to use it in my music production studio. It came preinstalled with Catalina and I am unable to run many apps without glitches and it doesn’t look like the companies will be releasing updates any time soon.

    1. I downloaded a copy of OSX Mojave on a secondary MacBook Pro 2012 running High Sierra and using DiskMaker app, created a bootable thumb drive with Mojave on it.
    2. I tried pressing option key while starting the system up and selecting the thumb drive consisting Mojave to boot and install the OS. To do this, I had to go into recovery mode and change the settings to allow the system to boot from an external drive.
    3. After the installation process starts and goes to the point where I need to choose which drive to install OSX Mojave on, it doesn’t allow installation on the internal SSD. It gives an error message stating an upgraded version of OSX is already running on this system.

    Can I get around this step by wiping the internal SSD containing Catalina? I see in the comments, some people have expressed it didn’t work for them. Any help in my case?

    1. Yes, as the article says, the file system on Catalina is different enough that it will choke the Mojave installer. You need to erase the _entire APFS Container_ before you can install Mojave on that Mac. Yes, you need to backup your data elsewhere first.

  11. Hello, thank you so much for this informative article!

    I ordered a new mac mini earlier this week, partly because I had found this article and it seemed feasible to downgrade to Mojave (and I need to work from home for the foreseeable future…). However, this morning I got an email from Apple informing me that my computer has been upgraded to the new Mac Mini released yesterday. So, now I’m concerned by the statement at the top of your article, that any new Mac models will not be able to downgrade to Mojave. Do you have any insight as to whether that applies to this new (seemingly minor) Mac Mini update? If so, I might quickly see if I can convince Apple to send me an older one.

    Thank you so much,
    Zubin

    1. Unfortunately, I do not have any insight. From the specs it looks as if Apple only bumped the base SSD storage. If the logic board remained the same, then you might still be able to downgrade. But we won’t know the exact differences between these models for sure until someone has them in their hands.

      1. Ok, that’s basically what I figured. Thank you so much for the prompt reply! Will report back after I receive it and try downgrading next week.

  12. hello,

    I bought a mac mini 2018 that came with Catalina. I need it to run High Sierra to try to then restore from the Time Machine backups I did on my MacBook pro 2011. Is this possible? I already have a bootable usb with High Sierra on it. The problem is after I select it to boot I get “the version of macOS on the selected disk needs to be reinstalled” – gives me two options Startup Disk and macOS Utilities. The first won’t find any startup disk and the second takes me to the Recovery menu with only the option to reinstall Catalina. Frustrating… Any suggestions?

      1. So this effectively means that if I want to clone my 10.13(sierra) Mac mini 2014 drive to the internal ssd of a 2018 Mac mini (via target disk mode) will not work? Mac mini 2018 which have the T2 chip will only work with Catalina/Mojave (depending on which OS was preinstalled?

  13. Can somebody please break this down a little easier for someone that’s not so tech savvy. I really need Step by Step break down to understand this. Anybody willing I would very grateful. I’m a music producer and need to use 32 Bit plug ins. Thank you again and hope to get a response.

  14. hi,
    what would be the possibilities with a new Macbook Air 9.1 – 2020 ??
    I’m sure this comes with Catalina, but I would prefer to stay on Mojave.
    cheers
    Fred

    1. Any new Mac models that Apple introduces from now on, will also require Catalina and cannot be downgraded to Mojave.

      The 2020 MacBook Air requires Catalina.

  15. Hi all, I got a new iMac 27 2019, with fusion 2tb, shipped with Catalina, and I would have liked to have it with Mojave.
    I built a mojave installer to an usb external disk, used cmd r to access Recovery, and deleted all internal disk. Then I restart pressing alt key to select the external disk. It let me do this, but after clicking on the installer icon the system showed a denied simbol, a circle with a bar.
    After that I tried cmd R and it started an Internet recovery, with a globe that was spinning forever.. After some tries I built a Catalina install external disk usb, and with it after a long time I succesfully install back Catalina.
    So, what did I do wrong?
    From what I read from this very clear post, I should create again the mojave installer usb disk, (but this time adding the –downloadassets), restart Catalina, press alt, select Mojave installer, and then? The Recovery partition of Mojave will pop up and from there I should delete all the internal disk, NOT restart but close recovery and then start installation of Mojave, right?

  16. Sorry, the phrase “NOT restart but close recovery and then start installation of Mojave, right?” should be read as “NOT restart but close disk utility, (NOT close recovery) and then start installation of Mojave, right?”
    Sorry, otherwise is the same error as before

    1. Yes, close Disk Utility and the start the Mojave installation. Be sure to delete the top level apfs container, not just the Catalina system volume.

  17. just to be sure, hoping not to have to repeat a nightmare, I have:
    Fusion
    Container disk2
    Macintosh HD
    Macintosh HD – Data
    I have to initialize the Container disk2, right?
    and then:
    1 recreate with a new name .. Container ?
    2 don’t do anything
    close disk utility

    1. yes, erase the Container. You can give it any name you want, that’ll be the name of your new system volume (it doesn’t actually name the container but the first volume inside the container).

      System volumes are still called “Macintosh HD” by default, which is a delightful anachronism.

  18. Start Mojave installation from alt key, gone to disk utilities..
    Not able to initialize Container.. gives an error “There has benn an internal state error”
    Operation not done
    and it remains as before.. what do I do wrong?

  19. Fixed..
    this is the way, basically initialize using hpfs journaled, then initialie again using apfs
    in detail:
    Recovery Mode, open Disk Utility.
    In the top-left corner of Disk Utility, click the View dropdown and select Show All Devices.
    Internal
    Fusion Drive
    Container disk 2 (1)
    Macintosh HD
    Macintosh HD – DATA

    1 The disk identifier may be another number.
    Select Container disk 2 in the sidebar and click the Erase icon in the toolbar.
    At the prompt, enter Macintosh HD for the Name – it will likely be pre-populated with Preboot – and select Mac OS Extended (Journaled) for the Format.
    Click the Erase button. Container disk 2 is deleted and the sidebar will show something similar to:

    Internal
    APPLE HDD ST1000DM003 Media
    APPLE SSD AP0032H Media
    Fusion Drive
    Macintosh HD

    Quit and then re-open Disk Utility to see the correct disk configuration:

    Internal
    Fusion Drive
    Macintosh HD

    now again using apfs instead of Mac OS Extended (Journaled)

    not so simple to put together, but now Mojave is back

  20. Hello I bought the MacBook Pro 16” it came with Catalina I am also looking to install the Mojave. I bought an external drive for it. I’m not quiet sure what else to do. I’ve tried following steps on YouTube I’m still clueless may someone please get back to me with all the details so I can know exactly what I am doing wrong? thank you!

    1. As I state in the post. The MacBook Pro 16″, and _all_ new Mac models that have been introduced since then (New Mac Pro, MacBook Air 2020, MacBook Pro 13″ 2020) _require_ Catalina and _cannot_ be downgraded to Mojave.

      Sorry.

      1. I believe you intended the second instance of “Catalina” to be “Mojave.” (Feel free to make the change and delete this comment.)

  21. Do you know whether a 16″ MacBook Pro can run a bootable clone of a pre-Catalina OS, with the clone on an external NVMe SSD? Thank you for putting this all together.

    1. from the post:

      The exceptions are […] the MacBook Pro 16“ and the Mac Pro (2019) which both require Catalina. You cannot use these instructions to force a Mac Pro or MacBook Pro 16” to boot to Mojave. Any new Mac models that Apple introduces from now on, will also require Catalina and cannot be downgraded to Mojave.

  22. Great article AB, thanks for sharing. I understand any new Mac/Macbook models that Apple introduces from now on, will also require Catalina and cannot be downgraded to Mojave.

    Do you think there’d be any issues trying to run Mojave through VirtualBox on the new Macbooks?

    1. In principle, no problems, that should work fine. Though I usually recommend using Parallels or VMware Fusion over VirtualBox. IMHO, the time and nerves you save getting a macOS based vm working and trouble shooting is worth the commercial license price.

  23. Any ideas about new iMacs 2020? The 23″ and new 27 (or maybe 29) surely will only use Catalina, right?

    1. Usually a Mac requires at least the version of macOS that the model shipped with when it was introduced.

  24. I just wanted to say thank you for this as well as the comments. You helped me plow through the Catalina nightmare. I own a recording studio and could never run my programs on Catalina. Your advice and direction were invaluable.

  25. I’m trying to downgrade a new (2108) MacMini which shipped with Catalina to High Sierra for a business that has incompatible software. I think that Mojave is as far back as this (new from box) Mac will go. I’d appreciate your thoughts.

    Also curious as to why my Mac mini (also 2018 running Catalina) responds as follows;
    softwareupdate –fetch-full-installer –full-installer-version 10.14.6

    Downloading and installing 10.14.6
 installer
    SUPreferenceManager: Failed to set object of class: __NSCFConstantString for key: LastRecommendedMajorOSBundleIdentifier with error: Error Domain=SUPreferenceManagerErrorDomain Code=1 “(null)”
    SUPreferenceManager: Failed to set object of class: __NSCFConstantString for key: LastRecommendedMajorOSBundleIdentifier with error: Error Domain=SUPreferenceManagerErrorDomain Code=1 “(null)”
    Install failed with error: Update not found

    Cheers

    Bill

    1. As mentioned in other comments, these error messages appear in 10.15.5. I have no idea what they mean and they don’t seem to break the tool.

  26. On my mid 2019 MacBook Pro 13 that shipped with Catalina, I installed Mojave on a separate APFS volume. Everything works fine…. Now that I am done, can I go back and delete the Catalina volumes (Macintosh HD & HD-Data), leaving only the Mojave Volume, without any problems?

  27. I just got a 2019 iMac that had Catalina installed.

    So it’s completely fine and safe (aka won’t void my warranty) to downgrade to Mojave?

    I absolutely hate Catalina which is why I bought the newest computer I could (2019 iMac) that could still be downgraded to Mojave.

    1. All I can tell you is that it _should_ work because Apple has not changed the hardware of the iMac since it was released. No-one can give you any guarantees or promises but Apple.

    2. Hi, I did it (iMac 2019 Catalina shipped, downgrade to Mojave) and it works.. it should work for You too.. You can read some of my messages above how I did it. And if You were not satisfied, using the internet recovery mode will give You Catalina back, as did to me first time I made it wrong.

  28. A happy “customer” checking in! I was getting despondent during the OS install after seven minutes of complete black on my monitor, but then it brightened with the initial Mojave screen on my new Mac mini. Now I’m about to do the information transfer from my old Mac that’s part of the initial setup.

    I used Fra_dta’s wrinkle of formatting first to Mac OS Extended (Journaled), then again to APFS. I figured it couldn’t hurt.

  29. I have a Mac Minni in my shopping cart. I have audio apps like a lot of people and would really like to stay Mojave! IS this current Mac Mini that is shipping still the same one for all intents and purposes. I was going to get the i7 with an additional 8 gig ram. Thanks…

    1. The Mac mini got a minor revision this spring where the base SSD capacity was upgraded. Other than that, the current Mac mini is still the same logic board and chipset that has been selling since October 2018. So it _should_ downgrade to Mojave. I have not been able to personally confirm this yet, since I haven’t had access to the very latest models.

  30. Procedure worked great for putting Mojave on a new Mac Mini 2020 (aka 2018 with the 256GB base SSD storage). Thanks!

  31. For my Mac Mini 2020 purchased in July 2020 from the Apple Online Store, I also managed to downgrade Catalina to Mojave

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