What is DMG?

Apple Disk Images are disk image files commonly used by the Mac OS X operating system. When opened, an Apple disk image is "mounted" as a volume within the Finder. Several Apple proprietary disk image formats can be used to create these images, including the Universal Disk Image Format (UDIF) and the New Disk Image Format (NDIF). Apple disk images usually have the .dmg file extension. In short words, a file with the DMG file extension is a Mac OS X Disk Image file.

Overview

1. Universal Disk Image Format (UDIF) is the native disk image format for Mac OS X; disk images in this format typically have a .dmg extension.

2. New Disk Image Format (NDIF) was the previous default disk image format in Mac OS 9,and disk images with this format generally have a .img or .smi file extension.

3. A previous version of the format, intended only for floppy disk images, is usually referred to as "Disk Copy 4.2" format.

4. Another similar format that supported compression of floppy disk images is called DART.

Support

Macintosh
Currently, the only way to open a .dmg disk image in Mac OS 9 is to use either the developer version of Disk Copy (version 6.4), or a beta version of the unreleased 6.5. However, both versions can only open uncompressed images; compressed Disk Images are unusable on Mac OS 9.

Non-Macintosh

dmg2img
DMGEXtractor
PeaZip
7zip

Related Software:

Macgo Mac Blu-ray Player: Display DMG format on your Mac.
Macgo Windows Blu-ray Player: Display DMG on Windows platforms.
Macgo Free Mac Media Player: Display DMG for Mac OS X.

Further Reading:

Visit Apple Disc Image on Wikipedia.
Learn more about How to open DMG files?