Note: This works for creating a bootable USB but may fail for clean installs on T2 Macs.
There are two primary methods for obtaining the Catalina installer officially. Note that Apple typically provides the installer as an .app bundle (Install macOS Catalina.app), not a raw DMG file. The conversion to DMG is a secondary step detailed in Section 3. mac os catalina download dmg
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume Use code with caution. Copied to clipboard macOS Catalina dmg file download for old macbook pro Note: This works for creating a bootable USB
softwareupdate --fetch-full-installer --full-installer-version 10.15.7 The conversion to DMG is a secondary step
Sites like archive.org , malwarebytes.com (not official), or random forums offer pre-made Catalina DMGs. In 2023, security firms discovered repackaged Catalina installers containing the Shlayer trojan – disguised as a “Catalina DMG downloader.”
: It replaced the "all-in-one" media app with dedicated apps for Music, TV, and Podcasts .