What is DMG file?

DMG file is the place to store applications in macOS. Open the DMG file, drag the application to the Applications folder , and then remove them. This limits you from the scary "Install Wizard" for most Windows applications. So, if the DMG file acts as a directory for an application, why do users have to use them instead of just downloading the application?

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Why does macOS use DMG files?

The main reason that MacOS uses DMG files is to make sure the file is properly downloaded and not spoofed. DMG files undergo a 'checksum', basically verifying that the file is 100% intact. This is what you see when the file is open:

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This small window first goes through a file verification phase and then, when it's sure it's a good file, the file will be moved to the decompression process. And that's the second reason macOS uses DMG files: They have a compressed format (like ZIP file) that makes the file size smaller. Saving data usage when downloading is always a good thing.

How to use DMG file?

Fortunately, MacOS does a great job of making things easy. All you really need to do is double click on the DMG file to open it, and mount it to your Mac.

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DMG mounts in two places: on the desktop and in the Finder sidebar in your hard drive. Click on either of these places to open the DMG file.

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When opening the DMG file, you will often see two things: Application and link to your application folder. Some DMG files - like Steam DMG are shown above - there are backgrounds that are styled for decorative purposes.

To install the application, drag the application to the Applications folder . It may take a second to copy, but when finished, you can launch the application from Launchpad or Spotlight just like any other application.

Note: Do not launch the application right from DMG. The application will no longer be available after you delete the DMG file.

Clean up

When you finish installing the application, you will have two copies, one in DMG format and one in the Applications folder . You can remove a copy of DMG because you no longer need it.

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First, remove the DMG file by right-clicking on it and selecting the 'Eject' command , or by pressing the eject button next to the drive in the Finder. This will unmount the DMG file from your system.

Next, delete the DMG file itself, unless you have a reason to keep it.

Can I use DMG file in Windows?

There are not many reasons why you want to use DMG files in Windows, because they often contain MacOS applications, not Windows applications. However, if you need to open a DMG file, 7-Zip supports extracting DMG files. If you want to convert DMG to another compressed format (such as converting DMG to ISO, like the DMG file format for Windows), a tool like DMG2img will help you get the job done.

Can you create your own DMG file?

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Yes, you can, and do so more useful than you think.

In addition to providing good compression level, DMG files also support AES 128 and 256 bit encryption, which means you can create a password-protected compressed folder.

Open Disk Utility and select File> New Image> Image from Folder (or Blank image if you want to create an empty DMG file that you can add content later). In the window that opens, select the folder you want to encrypt and click the "Choose" button .

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You will then have the opportunity to configure some additional options, such as whether to save the file and whether to use encryption. When you encrypt the folder, the Mac will prompt you to enter the password twice.

Also, by default, the DMG file can only be read, but if you want to read and write to the DMG file, change the 'Image Format' option to 'Compressed' to 'Read / Write'.

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When you open the new DMG file, it will prompt you to enter the password you selected. After entering the password, the DMG file will be mounted as any other file.

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Except for this time, DMG file is not just an application. It contains whatever you have stored there.

See more:

1. 3 tools to read DMG file extensions on a free Windows PC
2. Instructions for installing new fonts in Mac OS X
3. Instructions on how to transfer ESD file to ISO for Win XP, 7,8,10