Mac disk image formats on Windows: dmg, cdr, sparsebundle
A Mac disk image is a whole volume in a file. Disk Utility can make several kinds, and the extension (.dmg) often does not tell you which. Whether you can open one on Windows depends on how the data is stored inside.
The formats Disk Utility makes
Apple's descriptions, from the Disk Utility guide (checked October 30, 2026), and what Diskferry does with each:
| Format | Apple's description | Diskferry |
|---|---|---|
| RAW Image | "The data is stored in the image file exactly as it is laid down in the virtual disk" | Opens it |
| DVD/CD master (.cdr) | "It includes a copy of all sectors of the disk image, whether they're used or not" | Opens it |
| Read-only Compressed (ULFO) | "A read-only image that stores data in a compressed format" | Does not open it |
| Read-only (UDRO) | "A disk image that can't be changed after it is created" | Not tested |
| Sparse Bundle Image (UDSB) | "The data is stored in multiple files. This structure is often used for Time Machine backups over a network." | Does not open it |
| Apple Sparse Image (ASIF) | "A modern sparse read/write image" | Does not open it |
| Any encrypted image | Chosen in the Encryption menu | Does not open it |
Diskferry's Open a disk image button accepts .img, .dmg, .cdr, .iso, .bin and .raw files, and reads them as raw disks. A .sparsebundle is a folder of many band files, not a single file, so there is nothing to open. Disk images open without the administrator prompt that physical drives need.
Convert an image on a Mac first
If you have access to a Mac, Disk Utility can convert any of these into a format Diskferry reads: choose Images, Convert, pick the image, set Image Format to DVD/CD master or RAW Image, and set Encryption to none (Apple: convert a disk image). The converted image is as large as the volume inside it.
Without a Mac
- 7-Zip extracts DMG files and APFS images inside them; check the results, because in our test it wrote some compressed files as 0 bytes. Details
- TransMac lists "dmg, dmgpart, sparsebundle and sparseimage" among the image types it opens. TransMac compared
- An app installer .dmg holds a macOS program, which will not run on Windows whatever opens it. Opening a .dmg on Windows
Questions
How can I tell whether a .dmg is compressed?
Try it: Diskferry opens the file and, if it finds no APFS or Mac OS Extended volume, says so and mentions that compressed .dmg files are not supported yet. On a Mac, Disk Utility's Convert dialog shows and changes the format.
Can Diskferry open a Time Machine sparse bundle?
No. Sparse bundles are not supported, and Time Machine backups are not supported in this version either.
Last updated October 30, 2026. Still stuck? Support replies in person.
Related guides
- How to open a .dmg file on WindowsRaw disk images, compressed .dmg files and app installers are three different cases
- What is APFS? The Mac file system, explainedWhat APFS is, why Windows cannot read it, and what that means for your drive
- Open an encrypted APFS drive on WindowsPassword-protected Mac drives: what can be unlocked on a PC and what cannot
- Mac drive glossary for Windows usersAPFS, HFS+, container, EFI partition, T2, sparse bundle and more, in plain words
- Diskferry comparedMacDrive, Paragon, TransMac, HFSExplorer and the free options, with sources