Convert ISO to DMG

A DMG is useful when a Mac application, installer, or distribution workflow specifically expects an Apple disk image rather than an ISO. macOS can mount many ISO files directly, so conversion is mainly for packaging, compatibility with a particular tool, or local sharing without uploading the source image.

What the ISO format is

ISO is a sector-by-sector image of an optical disc, commonly used for operating-system installers, software discs, recovery media, and archival copies. An ISO can contain ISO 9660, Joliet, or UDF filesystems, boot sectors, and a partition layout. Windows and Linux users, software publishers, system administrators, and backup operators commonly use the format.

What the DMG format is

DMG is Apple’s disk-image format for macOS application downloads, installers, recovery media, and removable-disk images. macOS opens DMG files in Finder and mounts them with hdiutil. DMG images can be compressed, read-write, encrypted, checksummed, or stored sparsely; UDZO is a common compressed read-only format, while UDRW is a common read-write format.

A DMG does not turn Windows or Linux software into a macOS application. It changes the disk-image format while normally retaining the source filesystem and data.

How to convert the image on macOS

Using Terminal

1. Copy the ISO to a local drive and close any application that is writing to it.
2. Open Terminal and run:

hdiutil convert "/path/to/input.iso" -format UDZO -o "/path/to/output.dmg"

Replace both paths with the actual filenames. Quotation marks preserve spaces in paths. This creates a compressed, read-only DMG. To create a writable image instead, use:

hdiutil convert "/path/to/input.iso" -format UDRW -o "/path/to/output.dmg"

Inspect the result with:

hdiutil imageinfo "/path/to/output.dmg"

Test-mount it read-only with:

hdiutil attach -readonly "/path/to/output.dmg"

Detach the mounted volume with hdiutil detach "/Volumes/volume-name", replacing the volume path with the one displayed by the attach command.

Using Disk Utility

Open Disk Utility, choose File → Open Disk Image, and select the ISO. Select the opened image in the sidebar, choose Images → Convert, enter a destination, and select a compressed or read-only image format when available. Menu names and offered formats vary by macOS release; hdiutil provides more consistent control and is better suited to scripted conversions.

Using an online converter

Services such as Convertio and CloudConvert may offer ISO-to-DMG conversion, but supported image structures, maximum sizes, retention policies, and output formats can change. Upload only non-sensitive files: disk images may contain personal data, license information, proprietary software, or malware. Local conversion is preferable for large installers, copyrighted discs, bootable media, and confidential images. Some web services copy files into a new image rather than preserving the source sectors or boot metadata.

Compatibility and quality limits

Changing .iso to .dmg in the filename does not convert the file. A real conversion preserves the source contents in a different disk-image representation, but it does not add macOS compatibility or create a native macOS installer package.

Compression may reduce the output size when the image contains unused or repetitive data. It usually provides little reduction for already-compressed archives, videos, or installer packages. A bootable ISO may not remain bootable after conversion because boot support depends on its partition map, filesystem, firmware type, and the software used to write or mount the result.

After conversion, mount the DMG and inspect its files. For an image with an embedded checksum, run hdiutil verify "/path/to/output.dmg". To check that a transferred DMG was not altered, record its SHA-256 value with shasum -a 256 "/path/to/output.dmg"; this verifies the DMG file itself, not equivalence of its bytes to the original ISO.