A bootable USB drive is the most reliable way to install an older OS, especially for performing clean installations or troubleshooting.
*Note: macOS Sierra is no longer receiving security updates from Apple. Ensure you have a good antivirus and safe browsing habits if you use download macos sierra 1012 dmg file install
Simply downloading the .dmg does not give you the installer. You must "install" the installer: : Double-click InstallOS.dmg to mount it. A bootable USB drive is the most reliable
A bootable USB drive is the most reliable way to install an older OS, especially for performing clean installations or troubleshooting.
*Note: macOS Sierra is no longer receiving security updates from Apple. Ensure you have a good antivirus and safe browsing habits if you use
Simply downloading the .dmg does not give you the installer. You must "install" the installer: : Double-click InstallOS.dmg to mount it.