NOTE: I have included a Mac App Store download troubleshooting section in the middle of this article. We have to answer this question sometimes multiple times per week.
I usually hang out helping fellow MacAdmins in the #Catalina #Mojave and #HighSierra channels on. If you are a macOS user or just starting in Apple IT, you will find out pretty quickly this can get complicated. If you are wondering how to download macOS -OSX Big Sur, Catalina, Mojave or High Sierra installers you found the right place.
Do you need to download a full macOS installer? I will show you 7 different ways! How to download macOS Monterey 12, Big Sur 11, Catalina 10.15, Mojave 10.14, High Sierra 10.13, Sierra 10.12, 10.11 El Capitan, 10.10 Yosemite, 10.9 Mavericks, 10.8 Mountain Lion & 10.7 Lion!!!