Create disk image which can be read on Windows

I am interested in creating a disk image, using Disk Utility (or any other software) on macOS which can also be read on Windows.

Disk Utility provides the ability to create .dmg, .sparseimage, and .sparsebundle images all very conveniently. This is useful for me when I have a lot (such as a couple thousand) small files which I want to keep together for convenience purposes, but which is easy access to access and modify. Hence I use disk images (instead of disks), as they are single (or a small group of) files which can be mounted to reveal all the smaller files.

However, as far as I know, the disk images created with Disk Utility can only be read an modified only on macOS. I heard of a utility on Windows which viewing of .dmg images, but I remember this was a non-native, limited solution.

Is there a way to create such images on macOS, which is (preferably natively) compatible with Windows?

Yes you can actually create an .iSO image file on your Mac with Disk Utility and a little bit of Terminal magic.

Connect an external drive (or, if you have an older Mac, insert a disc into the CD/DVD drive) to your Mac and launch Disk Utility. This is the device that you will be placing your files on for conversion. A USB Drive is also useful if you can't find an empty Your disk will appear in the left column window.

Now that you’ve selected the source of the disc image, click on File > New > Disk Image from... In the popup window, select Desktop as your destination. Next, make sure to choose DVD/CD Master as the Image Format. Choosing this format ensures the contents of the disk are copied entirely as a .CDR image.

You should keep the image’s name short so that it’s easily reproduced.

If asked, enter your Mac password and hit OK to begin the disk image process. Depending on how large the disc is, the amount of time that’s necessary varies (Which makes USB drives very effecient). You’ll see a progress bar estimating the time until completion.

Once the process finishes, hit “Done,” and check your Desktop for the .CDR image. In its current state, the disk is ready for use on any Mac. To share the file with Windows users, you’ll need to convert it into a recognizable format. To do this, you’ll use your Mac’s Terminal app.

Assuming your .CDR file is on your Mac’s Desktop, open Terminal and type the following and hit the enter key:

cd desktop

Then, enter this line of code to transform the .CDR to .ISO and hit enter:

hdiutil makehybrid -iso -joliet -o [filename].iso [filename].cdr

Substitute both instances of [filename] with the name of your .cdr image. For example, I named my ISO file TEST-IMAGE, so the line of code I used is:

hdiutil makehybrid -iso -joliet -o TEST-IMAGE.iso TEST-IMAGE.cdr

Terminal will create a new hybrid image. This image can be used by both Windows and Mac computers that use ISO 9660 and HFS file systems.

An Image can be made from a folder which will can be mounted by both the macOS High Sierra and Windows 10 operation systems. (And perhaps older versions of these operating systems, but I did not test for this.)

The steps are given below.

1. Open the Disk Utility application.
2. From the menu bar select File->New Image->Image from Folder....
3. Select the folder the click on the Choose button.
4. Choose a name and where to save the image file. For Encryption: choose none and for Image Format: choose hybrid image (HFS+/ISO/UDF). Next, click on the Save button.
5. Rename the image file extension from .dmg to .iso.

The resulting image file can now be mounted by High Sierra and Windows 10.