MDF / MDS file format

.mdf · .mds · disk image · introduced 2002 by Alcohol Soft

What is a MDF / MDS file?

MDF (Media Descriptor File) and its companion MDS index are Alcohol 120%'s disc image pair. MDF holds the raw sector data, MDS the table of contents and copy-protection metadata. Together they preserve more of an original disc than ISO can — including subchannel data critical for backing up some game DVDs.

Most readers reach this page after double-clicking a .mdf file and finding their operating system unsure what to do with it. The good news: MDF / MDS is a well-understood format with mature tooling on every major platform. It is supported in one click by mainstream archivers on Windows, macOS, and Linux.

How to extract a MDF / MDS file

Opening a .mdf file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

Locate the .mdf file in File Explorer.
Right-click the file. If you have 7-Zip installed, choose 7-Zip → Extract Here. On Windows 11 the built-in extractor handles ZIP, 7z, RAR and several other formats directly through Extract All…
If prompted, pick a destination folder and click Extract.
The extracted files appear in a folder next to the original archive.

On macOS

Find the .mdf file in Finder.
Install The Unarchiver from the Mac App Store, or Keka for both creating and extracting.
Right-click the file → Open With → The Unarchiver (or just double-click after Unarchiver is set as the default).
The extracted folder appears next to the archive.

On Linux

Use your file manager: right-click the archive → Extract Here (file-roller on GNOME, Ark on KDE).

On the command line, run one of:

7z x archive.mdf    # works for almost any format

The files appear in the current directory.

How to create a MDF / MDS file

To pack files into a .mdf archive, you typically need an archiver that supports writing this format. Not every tool can create every format — for example, only WinRAR can create real RAR files. The sidebar lists the software known to read and write MDF / MDS.

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .mdf files.

If you regularly create archives at scale, a dedicated archive automation suite can wrap this command in scheduled jobs, integrity checks, and offsite replication.

Strengths

Preserves subchannel data
Handles audio and mixed-mode discs

Weaknesses and limitations

Two-file pair
Alcohol-centric tooling

Typical use cases

Game DVD backups
Discs with subchannel-based copy protection

Technical details

MDF / MDS uses the None (raw sectors) algorithm and is identified on disk by the magic byte sequence 4D 45 44 49 41 20 44 45 53 43 52 49 50 54 4F 52. The standard MIME type is application/x-alcohol-mdf. The format is a proprietary specification and is subject to license restrictions for some uses (notably creation).

Frequently asked questions

Is MDF / MDS safe to open?

Archive files are containers — they are only as safe as what they contain. A .mdf from a trusted source is fine; one received from a stranger can hold malicious executables, scripts, or files engineered to exploit bugs in your archiver. Always keep your archiver updated, and never run unknown executables that come out of an archive. A safe workflow is to extract into a sandbox and scan the contents before opening anything.

What is the maximum file size?

Modern implementations support archives in the multi-terabyte range. The practical limit is your filesystem (FAT32 caps at 4 GB; ext4, NTFS, APFS, and exFAT all comfortably handle multi-TB files).

Can I password-protect a MDF / MDS?

Some archivers can wrap MDF / MDS files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does MDF / MDS compare to other formats?

See our format comparison pages such as ZIP vs 7z, ZIP vs RAR, and tar.gz vs tar.xz for side-by-side feature tables.