Apple does not host a standalone "macOS Catalina.dmg" on a public website for direct browser download. Instead, they provide an "Install macOS Catalina" application that you can convert into a DMG.
If the file is called macOSCatalina.dmg you would drag and drop the file into the Terminal window after typing shasum -a 256 . macos catalina dmg direct download verified
softwareupdate --fetch-full-installer --full-installer-version 10.15 Apple Support Updates : Apple provides manual DMG downloads for update patches Apple does not host a standalone "macOS Catalina
The App Store downloads an .app file, not a .dmg . To convert it into a usable DMG file for virtualization or archiving, use the macOS Terminal: To download it directly, you can use the
As of this writing, Apple still hosts the official InstallMacOSCatalina.dmg on its secure servers. However, Apple does not make this link publicly browsable. To download it directly, you can use the following command-line method or a trusted download manager.
Type shasum -a 256 (Mac) or Get-FileHash (Windows PowerShell).