FormatDrop
Document Format

DMG

Apple Disk Image

DMG (Apple Disk Image) is macOS's native disk image format. Mac apps are distributed as DMG files; macOS users 'mount' them by double-clicking, drag the app to Applications, and unmount. DMG supports compression, encryption, and Apple's HFS+/APFS file systems — making it more flexible than ISO for Mac workflows.

What is DMG?

DMG files use the UDIF (Universal Disk Image Format) container, which can hold a file system image (HFS+, APFS, FAT, ISO 9660) along with metadata for compression (zlib, bzip2, LZMA), encryption (AES-128 or AES-256), and code signing. Modern DMGs are typically compressed and code-signed by the app developer for distribution via Gatekeeper.

DMG pros and cons

Advantages

  • Native macOS support — mount by double-clicking
  • Compression reduces download size (typically 50–70% of raw)
  • Encryption and password protection built-in
  • Code-signing integration with Gatekeeper
  • Perfect file system fidelity (HFS+/APFS)

Limitations

  • macOS-only — Windows requires HFSExplorer or 7-Zip
  • Cannot be burned to CD/DVD without conversion to ISO
  • Large for cross-platform distribution
  • Encrypted DMGs cannot be opened on non-Apple platforms

When should you convert DMG files?

Convert DMG to ISO for cross-platform distribution: `hdiutil convert input.dmg -format UDTO -o output.iso` on macOS, or `dmg2img input.dmg output.iso` on Linux. Convert to ZIP for simple file extraction without mounting. For bootable USB creation from a macOS installer DMG, use Disk Utility or `createinstallmedia`.

All FormatDrop conversions run entirely in your browser — no file upload, no server processing. Your files stay on your device.

DMG FAQ

How do I open a DMG file on Windows?
Use 7-Zip to extract files (read-only). For full mounting, use HFSExplorer (free) or paid tools like TransMac. For sharing across platforms, distribute as ZIP or ISO instead of DMG.
Why are DMG files so common for macOS apps?
DMG combines a complete app bundle, custom background images, EULA prompts, code signing, and compression in a single file. The 'drag to Applications folder' UX is a macOS convention that DMG enables. ZIP files don't support these features.
How do I create a DMG file from a folder on macOS?
`hdiutil create -volname "My App" -srcfolder /path/to/folder -ov -format UDZO output.dmg`. UDZO is the modern compressed format. For bootable installer DMGs, use Disk Utility's 'New Image From Folder' option.

More formats

HEICWebPAVIFEPUBWebMOpusMP3WAVM4AFLACAACMP4AVIMKVMOVJPGPNGGIFSVGTIFFICOBMPEPSARWOGGWMVPPTXPagesPDFDOCXRAWHEVCH.264AIFFM4VWMA3GPDNGRTFPSDOGVTSFLVAIXLSXCSVZIPAPNGMIDIJPEG XLMPG/MPEGVOBM2TSAC3ALACDTSJP2HEIFAPECBZ3G2SRTDOCPPTXLSODTODSM3URAR7ZM4BAMRTXTMOBITARGZJSONXMLYAMLKEYMTSCR2NEFMXFTGACAFASSVTTDSFRMF4VWVASFRMVBORFRW2EAC-3TTAISOXZDjVuFB2AUM4RAZW3MKAEXRVCFICSAAXPRCMP2SPXXSPFM3U8