This method is ideal for users who plan to install High Sierra directly on the same Mac used for downloading. However, if you need to create a bootable USB installer for a different Mac or if your current Mac is running a newer macOS version that prevents the download, you will need alternative methods.
This method is ideal for selling or giving away a Mac, starting completely fresh to resolve system issues, or upgrading from an outdated macOS version.
If you are downloading the macOS High Sierra DMG to perform a fresh install, you will also gain access to: Best Features of macOS High Sierra macos high sierra download dmg install
: Your Mac needs a minimum of 8 GB of available storage space, though 15–20 GB is recommended for a seamless installation.
Remember to consider the security implications of running an older operating system. If your Mac supports newer versions of macOS, upgrading to at least macOS Mojave (10.14) or Monterey (12) will provide ongoing security updates. However, for those who need High Sierra specifically — for legacy hardware or software compatibility — this guide provides everything you need to get it up and running. This method is ideal for users who plan
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Mount the newly created blank image to your system: hdiutil attach /tmp/HighSierra.dmg -noverify -mountpoint /Volumes/install_build If you are downloading the macOS High Sierra
Terminal will ask for confirmation before erasing the USB drive. Type Y and press Return to proceed. The process will take approximately 15–30 minutes, depending on your USB drive's speed. During this time, Terminal will display progress information, including when it erases the drive, copies the installer files, and makes the drive bootable.
If your Mac does not recognize the USB drive when you hold Option during startup, reformat the drive using Disk Utility with these exact settings: Mac OS Extended (Journaled) and GUID Partition Map. Then rerun the createinstallmedia command. Some users have success using a different USB drive, as not all drives are equally compatible with bootable creation tools.
Unlike newer versions of macOS that appear prominently in the App Store, High Sierra has been relegated to the "hidden" archives. If you search for it directly, you likely won't find it.
Now that you have a bootable USB installer, follow these steps to perform a clean installation of macOS High Sierra.