DMG File

What are DMG files and how to open them

Are you having problems opening a DMG file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your DMG files.

What is a DMG file?

A .DMG file is a Macintosh Disk image file.

A .dmg file is an Apple Disk Image used by macOS for packaging and distributing software, creating backups, or bundling files in a way that behaves like a virtual disk. When opened on a Mac, it appears as a mounted volume in Finder, letting the user browse files and copy or install them just as if inserting a removable drive. Many software developers distribute Mac applications inside .dmg packages, often with a drag-and-drop installer design.

The file is typically produced by Apple's Disk Utility or by command line tools like hdiutil, using the Universal Disk Image Format (UDIF). It can be set to read-only, compressed, read/write, or sparse (growing as data is added). Encryption may also be applied so the disk image prompts for a password before mounting. Once mounted, macOS treats the content like an actual disk volume.

A defining technical detail is a 512-byte trailer at the very end of the file (offset −512 from EOF) containing the ASCII signature "koly", which identifies it as a valid UDIF disk image.

How to open DMG files

We have identified four DMG openers that are compatible with this specific type of DMG file.

Programs that open Macintosh Disk image files

Last updated: August 10, 2026

Various apps that use files with this extension

These apps are known to open certain types of DMG files. Remember, different programs may use DMG files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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File.org helps thousands of users every day, and we would love to hear from you if you have additional information about DMG file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.