Free online IMG to DMG converter

A Mac application, backup workflow, or Disk Utility task may require a DMG instead of a raw IMG image. Converting the image provides a macOS-compatible container for mounting, distribution, or archiving, but it does not automatically change the filesystem or make incompatible contents usable on a Mac.

What the IMG format is

In the disk-image context, IMG usually means a raw, sector-by-sector image of a floppy disk, optical disc, partition, USB drive, or complete storage device. Imaging and backup utilities use IMG files for removable-media duplication, operating-system installation, retro-computing, and disk recovery.

A raw IMG can contain partition tables, boot sectors, filesystem structures, and file data without a separate container layer. The extension does not identify one fixed filesystem: an image may contain FAT, exFAT, HFS+, APFS, an ISO-style optical filesystem, or another layout.

Some optical-disc applications also use .img with companion .ccd and .sub files, notably CloneCD images. That variant is not necessarily a standalone raw image; preserving its disc layout may require the companion files and software that understands the CloneCD set.

What the DMG format is

DMG is Apple’s disk-image format, commonly used to distribute macOS applications, create removable-media images, store backups, and package mountable filesystems. Finder and Disk Utility can open many DMG variants and present their contents as mounted volumes.

DMG supports several image types, including read-only and read/write images, compressed images, encrypted images, and images with integrity checks. A compressed DMG can be smaller than the original IMG when its data is compressible or contains unused space, but conversion does not guarantee a size reduction.

How to convert IMG to DMG on macOS

Using hdiutil

macOS includes hdiutil, which can convert compatible raw images without additional software:

1. Make a backup copy of the IMG so the source remains unchanged.
2. Open Terminal and move to the directory containing the source, for example cd ~/Downloads.
3. Convert it to a compressed, read-only DMG:

hdiutil convert source.img -format UDZO -o converted.dmg

UDZO creates a zlib-compressed DMG suitable for distribution. To create a writable image instead, use:

hdiutil convert source.img -format UDRW -o converted.dmg

Inspect the output with hdiutil imageinfo converted.dmg. Test mounting with hdiutil attach converted.dmg, inspect the mounted volume, and eject it with hdiutil detach /Volumes/VolumeName, replacing VolumeName with the actual volume name. If the source is a CloneCD image, do not discard its .ccd and .sub companions; hdiutil may not preserve CloneCD-specific metadata or subchannel data.

Using 101convert.com

You can convert the file on 101convert.com for free without installing software. Upload the IMG, choose DMG as the output format, start the conversion, and download the result. Online conversion is unsuitable for confidential data, credentials, recovery images, licensed material, or very large disk images unless the service’s handling and size limits are acceptable.

Quality and compatibility limits

• For a normal raw IMG, conversion changes the image container and normally preserves the sectors, partitions, filesystem, and files. It does not convert an unsupported filesystem into a Mac-native one.
• A DMG is primarily supported by macOS. Windows and Linux may need third-party image software, and some applications cannot read compressed, encrypted, partitioned, or sparse DMGs.
• Bootability is not guaranteed. It depends on the retained partition map, filesystem, boot code, firmware mode, and the software or device that will boot the image.
• UDZO is read-only. Use UDRW when the mounted image must be changed, then convert the edited image to a compressed DMG for distribution.
• Conversion alone does not encrypt the result. Create an encrypted DMG separately when the image contains sensitive data.
• Always mount or inspect the converted image and compare important files with the source. A successful conversion command confirms that an output file was created, not that every filesystem, boot record, or optical-disc feature is usable.