Like when you try to download macOS High Sierra from the App Store or from the Apple website, it prompts to download macOS High Sierra’s some previous version or builds. After that, it will begin downloading to '/macOS Install Data' on the local machine. Click 'Continue', accept the licensing agreement, select the install drive, then the installer will prompt for an admin password. It will launch 'Install macOS High Sierra' after the download completes. From the App Store, grab the High Sierra installer. When you have downloaded them, you’ll have two packages. Step 1: Download the macOS Sierra package files from their respective URLs. If you’re new here, just follow the steps mentioned in this section to download macOS Sierra directly without the Mac App Store. Only, instead of one package, there are two this time. We’ll be repeatedly referring to these Apple OS versions below, so it’s good to know the basic macOS timeline.
Finally, if you want to run a parallel copy of Mac OS X on a virtual machine, you too will need a working installation file of an older Mac OS X. Also, you may have noticed your Mac’s performance went down right after the last update. To begin with, some of your apps may not be working properly (or simply crash) on newer operating systems.
There are many reasons that could point you to this radical decision. So, you’ve decided to download an older version of Mac OS X.