macOS
Shine a spotlight on the solutions to your most irritating Mac problems
You can’t run older macOS installer apps in recent version; install them from an external bootable installer disk instead.
Using 32-bit apps with Big Sur
Q I recently upgraded to Big Sur, but have now discovered that I need to use an old 32-bit app. What’s the best way to be able to run Mojave as well? by DAVID NELSON
A There are two good solutions, depending on whether you want simultaneous access to both the old app and your current ones. If you do, then you should run Mojave in a virtual machine from Parallels Desktop, VMware, or another virtualiser. This is quick to set up, and simplest in Parallels Desktop, which will install direct from a downloaded Mojave installer app, as listed at bit.ly/mac371macoslegacy.
If you don’t need that degree of access, but just want to be able to start up in Mojave occasionally, then you can install a copy on an external drive, or even, if you prefer, on a volume or in a container/partition on your internal storage.