What Is a DMG File?

A .DMG file is one of the many file types you will find when using a Mac. A .DMG file is a proprietary format, which means it is intended to be used solely with the Mac operating system, though it is possible for Windows and Linux users to enjoy the benefits of these files as well.

History

A .DMG file is a disk image file. This is a file containing the entire contents of a CD or DVD that have been compressed into one file on a computer. .DMG is a format invented by Apple and used primarily with the Mac operating system. The Windows equivalent of a .DMG file would be an .ISO file.

Security

One benefit a .DMG file has is that it can be encrypted. This means you can't open it or use it unless you have a specific password. This is a benefit that isn't even possible when burning files to a physical CD or DVD.

Function

Many users use .DMG files for sharing software over the Internet. As opposed to sending CDs and DVDs to someone, you can rip the contents of the disc to your computer, turn it into a .DMG file, and simply send one file over an Internet connection. These files are also easier to store since you can put them on a hard drive instead of trying to keep track of many different physical CDs and DVDs.

Disk Utility

If you want to create a .DMG file from a CD or DVD, you can do it on a Mac computer using a program called Disk Utility. You do not need to download anything to use Disk Utility---it is built into the operating system. Disk Utility can create .DMG files and also do the reverse by burning them onto a CD or DVD.

Considerations

.DMG files can also be opened by computers not running on the Mac operating system. Windows users can work with .DMG files by downloading a number of programs, including HFSExplorer and UltraISO. These are free programs that can be downloaded via the Internet. If you're running on a Linux operating system, you can download Cdrecord.