Mac OS – How to create a USB installer and downgrade

Given the fact that there are applications that are yet to be updated to be compatible with MacOS Big Sur, quite a few people saw a need to downgrade back to their older MacOS versions.

I will discuss how to create an external USB bootable drive for multiple MacOS versions and how to use this drive including on systems which have a T2 chip on them.

The Apple support links are as follows:

The free archiver Keka can be found at:

Let’s see how this works…