What Is a DMG File Extension?

The hundreds of different extensions that are given to files on computers can be overwhelming to the average computer user. Ten files could all be named identically and have different file extensions, which in turn makes them perform different functions. One of these many types of files is a .DMG file, used primarily on Macs. It is the Mac equivalent of an .ISO on a Windows machine. Use this article as a guide as you find out what a .DMG file extension is.



.DMG files are created by Apple computers and intended for use with the Mac operating system. These files are disc image files, which means they are the entire contents of a CD or DVD compressed down into one file. They can then be burned to a CD and DVD again at any time using a number of free pieces of software.


One benefit of .DMG files is that they can be password protected. You can convert a CD or DVD to a .DMG file and then put a lock on it so others cannot access it without the proper authentication. .DMG files are also compressed versions of CD and DVD information, which means they are actually smaller than the file size of the disc despite being the same physical information.


.DMG files are most commonly used for sharing entire programs over the Internet. The contents of a CD can be recorded to a .DMG file, at which point they can be shared over an Internet connection and burned to a CD once again.


If you are interested in creating .DMG files, you can do so easily by using programs that are built into the Mac operating system. These include Disk Utility and Disk Copy. You can also burn .DMG files to CDs and DVDs from within these programs.

Other Operating Systems

Despite being written for the Mac operating system, it is possible to use .DMG files on other systems. In Windows, you can open a .DMG using programs like PowerISO, UltraISO and IsoBuster. If you use the Linux operating system, a program called "cdrecord" can manage .DMG files. These are all free pieces of software that can be downloaded from the Internet.