Use the built-in createinstallmedia tool (replace Applications path if yours is different): sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/HighSierra --nointeraction 4. Unmount the Volume hdiutil detach /Volumes/Install\ macOS\ High\ Sierra 5. Convert to ISO Format
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How to Download and Create a macOS High Sierra ISO (2026 Guide) " Sarah said