Media Descriptor File
{{Short description|Disc image file format}}
{{Refimprove|date=December 2011}}
{{Infobox file format
| name = Media Descriptor File
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| extension = .mdf
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| genre = Disc image
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{{Infobox file format
| name = Media Descriptor
| icon =
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| extension = .mds
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| magic = MEDIA DESCRIPTOR
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| genre = Sidecar file
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Media Descriptor File (MDF) is a proprietary disc image file format developed for Alcohol 120%, an optical disc authoring program. Daemon Tools, CDemu, MagicISO, PowerDVD, and WinCDEmu can also read the MDF format.{{cite web|title=.MDF File Extension|url=http://www.fileinfo.com/extension/mdf|work=FileInfo.com|accessdate=11 December 2011|date=29 September 2009}}{{cite web|title=libMirage library|url=http://cdemu.sourceforge.net/about/libmirage|accessdate=1 August 2017}} A disc image is a computer file replica of the computer files and file system of an optical disc.
Unlike an ISO image{{Citation needed|date=December 2024}}, a Media Descriptor File can contain multiple layers (as used in dual-layer recording) and multiple optical disc tracks. Like the IMG file format, a Media Descriptor File is a "raw" image of an optical disc. The word raw implies that the copy is precise, bit-for-bit, including (where appropriate) file-system metadata.
A Media Descriptor File may be accompanied by a Media Descriptor Sidecar file. This optional binary file (with file extension .mds) contains metadata about an imaged optical disc, including a delineation of where disc layers begin and end ("layer breaks"), and which portions of the MDF belong in which disc layer. The MDS file also stores the location and value of the layer breach bit, a CD/DVD copy protection mechanism. The MDS file is comparable to the CloneCD Control File and cue sheet (.cue) file formats. However, their capabilities are not identical; also the cue sheet is a text file format.
Alcohol 120%'s MDF/MDS format is one of the few formats besides Nero's NRG, BIN/CUE and CloneCD's CCD/IMG/SUB disc image formats to support Mixed Mode CDs which contain audio CD tracks as well as data tracks.