: A popular open-source tool called Mist (macOS Installer Super Tool) allows you to download specific macOS firmwares and installers directly from Apple without compatibility restrictions.
If you are using a modern Mac running macOS Catalina, Big Sur, Monterey, or later, the App Store may block you from downloading older versions directly. You can bypass this restriction using the native Terminal application. Open (found in Applications > Utilities ). Type or paste the following command and press Enter :
Once the installer ( Install macOS High Sierra.app ) is in your folder, creating a bootable USB is the most reliable way to install or reinstall. Connect a USB drive (at least 16GB). macos high sierra download dmg install
from the recovery partition or USB installer
The preference pane will open, prompting a download confirmation. Click Download . : A popular open-source tool called Mist (macOS
Verify the current date. If it appears incorrect, use the date command to set it to a date before the certificate expiration.
Click "Erase" to format the drive. Once complete, the drive will be ready for the installer. Open (found in Applications > Utilities )
: A DMG file is a compressed disk image that contains either the full installer or a bootable system image. High Sierra DMG files are typically used for creating bootable USB installers, for immediate installation on a Mac, or for preparing installers for older or unsupported Macs. The authentic High Sierra DMG is approximately 4.9 GB.