What Is a DMG File?

This article describes what DMG files are, how to open one on various operating systems, and how to convert one to another archive format like ISO or IMG.

What Is a DMG File?

A file with the DMG file extension is an Apple Disk Image file, or sometimes called a Mac OS X Disk Image file, which is basically a digital reconstruction of a physical disc.

For this reason, a DMG is often the file format used to store compressed software installers instead of having to use a physical disc. You'll most likely only see them when downloading macOS software from the internet.

This macOS disk image format supports compression, file spanning, and encryption, so some DMG files might be password protected.

Versions of Mac newer than OS X 9 support DMG files, while the older Mac OS Classic uses the IMG file format for the same purpose.

How to Open a DMG File on a Mac

DMG files are intended for Macs, so opening one on a Mac is very simple.

A DMG file is "mounted" as a drive and is treated by the operating system as if it were a physical hard drive, making it really easy to view its contents. The software you download for your Mac in a DMG format can be opened like any other file on a Mac, and then the setup program can be run to install the software.

How to Open a DMG File in Windows

A DMG file can certainly be opened in Windows, but that doesn't mean you can actually use anything you find within it.

For example, say a DMG file isn't just storing compressed files like images and videos but is instead holding a software program. You can extract/open the DMG file in Windows using one of the programs mentioned below, but you can't actually execute the program and use it like you would another Windows application. To use the same program in Windows, you need to download the Windows version, not the Mac DMG version.

However, assuming the DMG file just contains files like images or videos (which are likely in a format that's also compatible with Windows), or you want to just see what's inside the DMG file, you should have no problem using one of the below programs to view them.

Windows can open a DMG file with any compression/decompression program, such as the best free zip and unzip programs that support the format.

Visit the DMG Extractor website to learn about the DMB Extractor paid version, which is helpful if you need to do more with DMG files than just uncompress them.

Go to the DMG Viewer website to learn about and download this free tool that can help you see what's in the DMG file. Visit the Catacombae HFSExplorer to learn about and download this free tool for viewing DMG files on Windows (and Linux); it also lets you create new DMG files.

The dmg2iso tool that will convert the DMG image file to an ISO image file, which is much more usable in Windows. If you need to mount a DMG file in Windows, but don't want to convert it to ISO first, a few programs do support this. Check out these tools on WinCDEmu and the Pismo File Mount Audit Package download page. Newer versions of Windows support ISO mounting natively.

How to Convert a DMG File

As we mentioned above, dmg2iso can be used to convert DMG to ISO. dm2iso is a command-line tool, so you may need to reference the download page (see above) for instructions on the syntax and other rules. Also on the download page is a DMG to the IMG tool if you need to convert the file to an IMG file instead.

Visit the AnyToISO download page for the AnyToISO tool, which works the same way as dmg2iso but is much easier to use. The program is free but only for files that are no larger than 870 MB.

Some free file converters can convert DMG files to a variety of other archive formats, like ZIP, 7Z, TAR, GZ, RAR, and others. CloudConvert and FileZigZag are two notable examples.

To convert DMG to PKG (a macOS installer package file) requires that you first extract the contents of the DMG file and then build a new PKG file using that data.

You cannot convert DMG to an EXE file if you want to use the DMG file in Windows. DMG files are for Mac and EXE files are for Windows, so the only way to use a DMG program on Windows is to download its equivalent from the developer (if one exists); there aren't any DMG file to EXE file converters.

If you want to make a bootable DMG file, you don't have to worry about converting it to a USB format with any of the tools mentioned above. The whole DMG to USB process is possible with a tool like TransMac (available via the TransMac download page). Just right-click the USB drive in that program and choose Restore with Disk Image, and then you can boot from the USB drive to run the DMG program.

Still Can't Open the File?

If none of the techniques mentioned above have been helpful in opening the DMG file in Windows, macOS, or Linux, there's a really good chance that you don't really have a DMG file. This might happen if the file extension has been confused for DMG.

For example, the DGML file extension looks a lot like DMG even though the two are unrelated. The former is used for Visual Studio Directed Graph Document files and opens with Microsoft's Visual Studio.

GMD is another example of a similar-looking suffix that's reserved for GameMaker Program Code files and GroupMail Message files. Again, neither format is related to the DMG Mac file format, so if your file really ends in one of those extensions, you need GameMaker or GroupMail installed in order to use the file.

Frequently Asked Questions

• How do you burn a DMG file to DVD? You can burn disc images directly from Finder. Insert a blank disc in your DVD writer and open the folder in Finder containing the DMG file. Right-click the file, select Burn Disk Image > Burn.
• How do you convert a DMG file to an IPSW file? An IPSW file is an archive file format that stores encrypted DMG files. You can convert a DMG to an IPSW file using a third-party file extractor application, such as 7-Zip or PowerISO. Open the DMG file in the file extractor, select Extract, and choose IPSW as the format.