If you are on a newer Mac, you can bypass the App Store completely by using the Terminal app:
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/Catalina --nointeraction
The Ultimate Guide to Download macOS Catalina 10.15 ISO and DMG Images download macos catalina 10.15 iso and dmg image
Last updated: 2026. This guide complies with Apple’s software license agreement for personal, non-commercial use.
Eject the finished installer volume safely before converting it: hdiutil detach /Volumes/Install\ macOS\ Catalina Use code with caution. 5. Convert DMG to ISO format If you are on a newer Mac, you
The official way to get the full installer is through the Mac App Store or Terminal on a compatible Mac .
Apple signs its official installers with strict . : The download typically requires about 20 GB
: The download typically requires about 20 GB of free space and at least 4 GB of RAM.
Click to create a machine. Set the Type to Mac OS X and the Version to Mac OS X (64-bit) .