Chapter in this post:
If you want to install Mac OS X or macOS on an Apple Mac, you need the corresponding installation file - the so-called "Installer". Where you can download (older) Mac operating systems, I've already given you that in this guide shown. Instead of the full installer with several GB in size, however, sometimes only a few MB file is downloaded, which loads the rest from the Internet when it is executed. That's stupid if you want to work on a Mac without an Internet connection or on several devices - you will find the solution here.
For example, if you want to download the 2017 operating system macOS 10.13 High Sierra as a complete installation file, then you should see from the size whether that worked. Because then the file is about 5 gigabytes in size. If you only got the installation help from the App Store, it only measures around 19 or 20 megabytes.
In order to carry out an installation on several Mac computers or on a Mac, iMac or MacBook without an Internet connection, you need the entire macOS High Sierra Installer. And you can get it via the third-party app "macOS High Sierra Patcher Tool for Unsupported Macs" (Link) from DosDude1. I have already described its software to you here: Install macOS Mojave on old, unsupported Macs.
If you have used the link above (or the one listed below) and downloaded the patcher app, then open it. It may be that you have to enable permissions via the settings of the Mac, iMac or MacBook, as this is a third-party offer. If the software is running on your computer, these are the steps to take:
Boot stick help: Articles about bootable USB sticks
On the DosDude1 website you will find an overview of other patcher apps in addition to the software page for the High Sierra Patcher linked above: Click here. This includes a macOS Catalina patcher, which is intended to install the 10.15 version, which will be released in autumn 2019, on older, actually unsupported Apple Mac models.
With the versions for 10.12 Sierra, 10.14 Mojave and later also 10.15 Catalina, you can download the full installer using the same procedure as for 10.13 High Sierra. If you only get the help file measuring a few MB via the App Store, this may be exactly the solution you have been looking for to get the complete file measuring several GB;)
Effectively for free: iPhone 13 Mini and iPhone 13 deals with top conditions at Otelo - Advertisement
Jens has been running the blog since 2012. He appears as Sir Apfelot for his readers and helps them with problems of a technical nature. In his free time he drives electric unicycles, takes photos (preferably with his iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions for current bugs.