How can I install macOS version 11.2.3 (Build 20D91) (or older version of Big Sur, such as the one it came with) on a partition or volume (that I've already created) my M1 Mac?

I've tried multiple ways and nothing is working, and Apple hasn't been helpful so far, by phone or at the Genius Bar.

I'm astonished I get 0 hits with this google search: https://www.google.com/search?q=%22Restore+image+for+macOS+version%22+11.2.3+(Build+20D91)+%22is+not+supported+on+this+machine%22

Some background: The M1 Mac was ordered directly from Apple and arrived March 31, 2021, and so certainly can't have come with a version newer than 11.2.3. 11.2.3 was the latest production version of macOS on March 31, 2021.

I found an interesting clue!

nvram -p says: ota-original-base-os-version 21G83

This is odd; this is way off - this is a very recent version of macOS - 12.5.1, as in UniversalMac_12.5.1_21G83_Restore.ipsw

Does anyone have any idea if it makes sense to change this setting?

I tried nvram ota-original-base-os-version=20D91 but it hasn't made a difference.

*My M1 Mac is happy to download Big Sur using the link Glyph provided, unlike his: But this is newer than the version I want to install anyway. Screenshot of the Software Update preferences panel downloading Big Sur

I wonder what the cause for this difference is; could be a lead.

  • If your Mac didn’t come with that version previously, you cannot install it. Your Mac will only support that version and up.
    – Allan
    Dec 19, 2022 at 22:51
  • 1
    @mark-wilson Indeed - Apple Support wrongly said my Mac (2020 M1 MacBook Air) came with 10.15.3 (or I mis-transcribed it.) Thank for catching that. It was ordered directly from Apple and arrived March 31, 2021 and can't have come with a version newer than 11.2.3, of that I'm certain. 11.2.3 was the latest OS on March 31, 2021 per en.wikipedia.org/wiki/MacOS_Big_Sur , and I recall the OS needed updating when I first got the Mac. And I have the receipt in my email. Dec 20, 2022 at 1:39
  • You kind of lost me with your comment so, if my response here is off, please forgive me. Anyway, if 11.2.3 is not newer than what your Mac came with, it’s older and thus cannot be installed.
    – Allan
    Dec 20, 2022 at 2:30
  • @Allan Sorry, that was confusing; let me rephrase. 1) I should be able to (bare-metal-) install what it came with. Agreed? 2) An M1 Mac that arrived March 31, 2021 can't have come with a version newer than 11.2.3. Agreed? 3) An OS as new or a bit newer than what it came with, specifically 11.2.3, should be installable. Agreed? Dec 20, 2022 at 2:58
  • 1 - yes. 2 - technically yes, but a manufacturer can install pre-release versions on hardware or modify the actual supported version via OTA. 3 - technically yes, but see #2.
    – Allan
    Dec 20, 2022 at 3:10

3 Answers 3


Downgrading an Apple Silicon Mac is generally not possible. You need to revive or restore it from another Mac to ensure the firmware matches the OS and the installer.

I'm assuming you have a very, very good reason to attempt to dual boot or run on hardware this OS only. If not, you would be better suited with virtualization to run the "older" OS and let your Mac ride the firmer, recovery OS, macOS normal upgrade train.

There's lots of good writing on the internet as people upgraded to betas, downgraded back to production and more. I haven't seen any that contemplated the nvram or partition scheme as a good plan and most I know of ended up needing to wipe and run one OS at one time on their Apple Silicon Macs. The new filesystem, boot, recovery and T2 / processors make the old way of attempting this not technically sound.

  • I am curious what virtualization solution you’d recommend that is capable of guesting big sur?
    – Glyph
    Dec 20, 2022 at 4:07
  • Thanks. When I bought it, I was under the impression that it was NOT locked down like an iPhone and am not happy to learn that in important ways it is. Certainly there are up-sides, mainly better security. But this block strikes me as an unnecessary restriction that is inconsistent with advertising that one can, for example, choose to install and run software of one's choice on a Mac, not just that approved for sale in the Apple App Store. I don't see how the steps Apple outlines for reviving or restoring at the link Apple you provide would get me closer to having 11.2.3 installed. Dec 20, 2022 at 16:02
  • But again, thanks. It seems like IF I could find someone who still has the old OS installed, and copied the partition over, like with CCC (Carbon Copy Cloner), that would work. Yes? But by effectively limiting my choice to this, Apple does the opposite of improving security, by forcing me to use a low-security source for the OS, instead of getting it from Apple directly. Odd, no? Also, what Glyph beat me to asking! It effectively leads to these questions - any virtualization solution has to end up with an installation of this old OS! ... Dec 20, 2022 at 16:09
  • I've been purposely avoiding looking for, for example, docker installs, precisely because of the security risk of obtaining an (intentionally or inadvertently) trojaned copy of the OS. Dec 20, 2022 at 16:11
  • I already have two different macOS installations on my Mac - it's worked fine for me to have the production OS and a beta OS installed. I'm just wanting to install this third OS. Dec 20, 2022 at 16:16

You will find that virtualization options specifically do not support anything less than Monterey on Apple Silicon (https://kb.parallels.com/en/124223, https://github.com/insidegui/VirtualBuddy/blob/main/README.md, https://docs.getutm.app/guest-support/macos/), due to the absence of the virtualization framework that makes this possible. Virtualization wasn't even allowed until Big Sur https://www.macstadium.com/blog/developers-big-sur-and-vindication and so it was not super well supported on the new hardware.

There were bugs in Big Sur which caused physical damage to the mac, so while these were nominally fixed https://9to5mac.com/2021/02/25/macos-big-sur-11-2-2-usb-c-charger-fix/ it makes sense that apple might be cagier than usual about this particular downgrade. The link from Apple's own download page, https://support.apple.com/en-us/HT211683, to Big Sur won't download for me on any Apple Silicon computer.

Impossible to prove a negative, but I think you're out of luck. It might be useful to know why you want to do this?

  • Also, This is helpful but isn't really an answer to the main question. I've been trying to install it directly by booting off an installer; I only tried virtualOS because that wasn't working. 11.2.3 shouldn't have fixes for any bugs that were identified as causing physical damage. Dec 20, 2022 at 2:04
  • The first three links show those versions of those virtualization apps don't support anything less than Monterey on Apple Silicon, but don't say anything about it being impossible. Virtualization of macOS long predates Big Sur, and is officially allowed: "D. Virtualization. ... may install, use and run additional copies or instances of the Apple Software within virtual operating system environments in accordance with Section 2B(iii), ... - apple.com/legal/sla/docs/macOSBigSur.pdf Dec 20, 2022 at 2:23
  • (My M1 Mac is happy to download Big Sur using the link you provided. But this is newer than the version I want to install anyway.) Dec 20, 2022 at 2:36
  • Also, Apple is still making 11.2.3 available, e.g. via the link in my question. But they're blocking attempts to install it. Dec 20, 2022 at 2:45
  • Re: it being impossible, sure, maybe it’s possible somewhere, but the fact that so many don’t support it is a hint about the underlying issues. Here’s vmware’s page, also noting they only support it on x86_64: vmware.com/resources/compatibility/…
    – Glyph
    Dec 20, 2022 at 4:11

According to @bmike: "You can relax the boot security and bring any OS you please to the hardware - all this is documented in the Apple Platform Security guide and this KB, @WHO'sNoToOldRx4CovidIsMurder"

(Putting this answer here as, even though it doesn't work for me, even with Genius Bar help, it's the documented answer.)

  • Why the downvotes? Aug 19, 2023 at 21:53
  • Looking again, I think I (and the Genius Bar folks) missed the "Note: Security downgrades aren’t allowed on the paired recoveryOS LocalPolicy" part and need to use Fallback recoveryOS: "From a shutdown state, double-press and hold the power button." Testing. Aug 19, 2023 at 22:00
  • Didn’t help. 😡 Can’t tell the difference between Fallback recoveryOS and paired recoveryOS. Aug 24, 2023 at 22:19

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