This method uses the official createinstallmedia command in Terminal, which is built right into the macOS installer.
For a standard installation, the goal is to get the official installer from Apple. While the Mac App Store is the most common method, it has a significant limitation: . If you're on a newer Mac, the App Store might not let you download High Sierra.
Upgrading older Macs directly to newer OS versions without stepping through High Sierra first can cause firmware conflicts.
On Macs running macOS Catalina 10.15 or later, you can download the full installer directly using the command line: Open .
This command tells macOS to download the full 5.2GB installer package directly from Apple’s content delivery network.
Complete Guide: How to Download macOS High Sierra 10.13.6 DMG and Install It
