What is DMG format?

DMG (Apple Disk Image)

DMG is Apple's disk image format, used throughout macOS to represent a virtual disk as a single file. When opened, a DMG file mounts on the desktop just like a physical drive, making it the standard way Mac software is packaged and distributed — most third-party Mac applications you download arrive as a DMG containing the app and an installer shortcut.

Beyond software distribution, DMG files are used for creating disk backups, transferring large collections of files while preserving Mac-specific metadata and permissions, and even for running encrypted, password-protected virtual disks. macOS supports several internal formats within a DMG, including compressed (read-only) and sparse (dynamically growing) disk images.

Because DMG is deeply integrated into macOS, it mounts and handles natively without any additional software on a Mac. On other platforms, however, opening a DMG typically requires specialized tools, since Windows and Linux don't have built-in support for Apple's disk image format.

DMG files can also be signed and notarized by Apple as part of macOS's security model, which is why official app downloads for macOS are almost always distributed this way rather than as a plain ZIP or installer executable.

While DMG is the natural choice for anything Mac-native, its limited support outside macOS makes it less convenient when sharing files with Windows or Linux users, who will need extra software to access its contents.

What programs can open DMG format?

  • Disk Utility (macOS)
  • The Unarchiver
  • 7-Zip
  • PeaZip
  • dmg2img
  • HFSExplorer
  • Finder (macOS)

Use cases for DMG format?

  • Distributing macOS software installers
  • Creating compressed Mac disk backups
  • Mounting virtual disks on macOS
  • Transferring files while preserving Mac-specific permissions
  • Creating encrypted, password-protected virtual disks
  • Packaging notarized apps for macOS distribution
  • Archiving large collections of Mac files
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