How to Create an Encrypted Disk Image on Mac

When you want to create a security for the sensitive files on your Mac, many of you usually choose the third party utilities like VeraCrypt to help you.  But you might not know that you can take advantage of the built-in Disk Utility to create an encrypted disk image.

To be fair, using the built-in BitLocker feature can also help you create an encrypted container, but the process requires you a Professional or Enterprise edition. However, the trick we are going to show you below works on any Mac device. Once you create an encrypted disk image, you can easily mount the image file and access to your stuff. Whenever you want to get access to your files, simply unmount the image file. Here is how to create an encrypted disk image on your Mac.

How To Create an Encrypted Disk Image

First, you need to open the Disk Utility app. Next, open a Finder window, click on “Applications” and double-click on the “Utilities” folder. From there, click on the “Disk Utility” item. You can also press Command + Space keys to launch the Spotlight search and type the “Disk Utility” into the search box. Next, press Return to open it.

From the Disk Utility window, go to File > New Image > Blank Image.

The process will create a new disk image (.dmg) file. Here are the options for you to configure:

  • Save As: Set a file name for the disk image file.
  • Name: Name the disk image file. This name is a description.
  • Size: Select a size for your disk image file. For instance, if you create a 100 MB disk image file, it will take up 100 MB of hard drive space, even when you have not moved any files inside it. You can also then enlarge or shrink the disk image if you want.
  • Format: Choose Mac OS Extended as the file system.
  • Encryption: There are two options: 128-bit or 256-bit AES encryption. Although 256-bit is more secure, 128-bit is faster. If you worry about the sensitive files, you should choose 256-bit and accept the slight slow-down for the better security.
  • Partitions: Choose “Single partition – GUID Map” to use a single partition.
  • Image Format: Choose “read/write disk image” to read from or write the disk image.


If you choose for an encrypted drive, you are prompted to create a password for the disk image. You should set a strong password by clicking on the “Key” button to create a strong one.

In case you lose the password, you will also lose the access to the files inside the encrypted disk image. So, you should set a memorable password.

You probably check the “Remember password in my keychain” option. The option remembers the password in your account’s keychain so it will automatically fill in the future. If you don’t want anyone to access your encrypted container, just uncheck that option.

You can find the disk image on your desktop or in the Finder under Devices. If you want to encrypt files, just save them to your device. To unmount the encrypted disk image, click on the Eject button in Finder or right-click on its desktop icon and choose the “Eject” command.

How to Mount an Encrypted Disk Image

If you want to mount the encrypted disk image, locate the file on your hard drive with the .dmg file format. Simply double-click on it. You’ll be prompted for entering the encryption password that you provided during the setup process.


After entering the password, you can easily access the contents of the file as the way you access other disk images.

Also read: How to check Mac’s free hard drive space

How to Enlarge or Shrink an Encrypted Disk Image

If your encrypted disk image runs out of space but you don’t want to create a new one, you can easily enlarge the current disk image. Or in case you don’t use the full size of the disk image, just shrink it to get more space for your hard drive. To do so,

  • Launch Disk Utility, navigate to Images > Resize
  • You’ll be asked for entering the encryption password.


Keep in mind that you cannot resize the disk image if it’s being mounted. Once you grayed out the Resize Image button, from the Disk Utility window, click on the Eject button in and try it again.

After that, you can now do with the encrypted .dmg file as your liking. You case save it on your hard drive, copy it into a USB drive, or even store it online on the cloud service like Google Drive.


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