If the App Store is giving you trouble, you can use the Terminal to fetch the installer directly from Apple's servers:
I have included a critical safety disclaimer at the top, as distributing copyrighted DMG files can be legally risky, and downloading macOS from third-party sites is dangerous for users.
Open your web browser and go to the official Apple support page for older macOS versions. Click the link for . Mac Os Catalina 10.15 7 Dmg Download
macOS Catalina 10.15.7 is the final stable release of the Catalina series, originally launched by Apple on October 7, 2019. While Apple typically provides macOS as an installer application ( ) rather than a direct Disk Image ( , users often seek the DMG format for creating bootable USB drives , setting up virtual machines , or performing clean installs on older hardware. How to Obtain the macOS Catalina Installer
softwareupdate --fetch-full-installer --full-installer-version 10.15.7 3. Creating a DMG from the App File If the App Store is giving you trouble,
Once complete, the file Install macOS Catalina.app will be located in your folder. Using the Terminal (macOS Mojave or Newer)
Third-party DMGs can be injected with malware or spyware. macOS Catalina 10
Note: Apple no longer shows Catalina in search results for most accounts. You can use this direct App Store link (paste into Safari): macappstores://apps.apple.com/us/app/macos-catalina/id1466841314?mt=12
For users already on 10.15, you can download the macOS Catalina 10.15.7 Combo Update or the Standard Update directly from Apple's support website to patch your system. System Requirements Download macOS Catalina 10.15.7 Update - Apple Support
Apple provides the .app installer, but if you specifically need a .dmg , you can convert it using the tool: Open Disk Utility. Go to File > New Image > Image from Folder . Select the "Install macOS Catalina" app. Choose "read/write" and save it as a DMG. What’s New in 10.15.7?
True standalone DMG files of the full OS are rare because Apple distributes the OS as an .app package inside a DMG for older versions via the "Software Update" mechanism.