Installing Older MacOS on client than what it shipped with


I am wondering if anyone has discovered a way to install an older MacOS on a client than what Apple shipped it with? We have purchased some Intel Macbook Pro’s and they came with Big Sur installed. I need to back them down to Catalina if possible.

I know the official word from Apple is that this cannot be done due to the firmware settings. I didn’t know if anyone had figured out a workaround. My only other concern would be if the workaround would void the Apple Care coverage?

Thank you!

It’s not officially supported to downgrade below the shipping version of
MacOS, so if you were to take a device in for AppleCare the first thing
they would do is tell you you’re running an unsupported OS and re-install
an appropriate operating system.

That said, if you’re using a device which has drivers included in Catalina
and has been tested with Catalina (macOS Catalina is compatible with these
computers - Apple Support I
don’t really see an issue with downgrading if you have some genuine need to
run an operating system that’s already halfway through its support
lifecycle on new hardware.

Hello Alex,

Thank you for the response.

The challenge I am facing is finding the workaround to downgrade this client. None of the standard instructions from Apple work in this situation. I have downgraded a few clients in our environment successfully, but those clients shipped with either Mojave or Catalina. This is the first shipment that I have received with the Intel chip and running Big Sur.

Thank you.

It’s a pretty lengthy process, as you need to disable the T2 chip’s secure
boot functionality first, and completely erase the SSD.

Alex is right. Simplest way is to download the Catalina installer from Apple here: How to create a bootable installer for macOS - Apple Support
and install on external hard drive. Install a copy of the Catalina installer on this external drive. Boot the offending machine from the external drive after disabling the T2 chip. Install Catalina on internal drive.

Hello Alex and Russ,

From what I can see and have done, those are the steps that I have done and it doesn’t work because the laptop was shipped to me with Big Sur already installed. Apple official position is that you cannot change a laptop to a lower OS than what is shipped with. Since it was shipped to me with Big Sur, it is not “going back” to Catalina.

I was hoping someone had figured out some other way to force a client to the older OS version.

Thank you

What model device are you trying to downgrade? Is it on the list?