Open Terminal and run:
: Open the macOS Catalina page on the Mac App Store. Click Get , which will open Software Update in your System Preferences to begin the download. download macos catalina 10.15.7 dmg
Most users looking for a DMG actually intend to create a bootable USB drive to install the OS on a fresh Mac. A DMG alone cannot boot a computer; it needs to be written to a drive. Open Terminal and run: : Open the macOS
If you bypass the official methods and download a pre-made DMG from a "warez" site or a forum, you walk a dangerous path. Modified DMGs can contain scripts that compromise your Mac's security. A DMG alone cannot boot a computer; it
: Use the Apple Support Download page to get the "Combo" DMG, which can update any previous version of Catalina to 10.15.7.
For advanced users, Apple’s hidden command-line tool can fetch the installer directly.