MDS file format is a binary file with the magic number "MEDIA DESCRIPTOR" appearing in the beginning of the file. The MDS file contains metadata about the original media, specifically the position of the layer breaks or layer breach bit, a property of the copy protection feature of DVDs. An MDS file is then used in conjunction with its related disc image to re-create the DVD. It is called an MDS file because of its implemented file extension .mds. It could also be described as being an archive file of MDS format.
MDS file can be created by optical disc imaging applications. The MDS file format is primarily utilized by the commercial application Alcohol 120%. However, it was also used by DVD Decrypter (now ImgBurn) which has since been released to Macrovision by its original author, Lightning UK!. It is presently used in limited fashion by Lightning UK. ImgBurn. Daemon Tools also uses this format to mount/emulate MDS files. CDemu allows the MDS files to be used under Linux.