The space where something used to be.
Before installing any new operating system, it's crucial to back up your data.
If you are looking for the official, secure version of macOS 10.13.5, it is best to use Apple's verified channels.
: You can find various macOS High Sierra images, including ISO formats , which are useful for virtual machines. How to Use an .rdr Image File
Then the desktop flashes.
: Click "Get" or "Download." This will download a file named "Install macOS High Sierra" into your Applications folder.
You hit Enter.