Distribution Media Format (DMF) is a format for floppy disks that Microsoft used to distribute software. It allowed the disk to contain 1680 kB of data on a 3½-inch disk, instead of the standard 1440 kB. As a side effect, utilities had to specially support the format in order to read and write the disks, which made copying of products distributed on this media more difficult. Macintosh running Disk Copy 6.3.3 on Mac OS 7.6 or later can copy and make DMF disks. The first Microsoft software product that uses DMF for distribution were the 'c' revisions of Office 4.x. It also was the first software product to use CAB files (then called "Diamond").
Comparison of DMF and standard 1440 kB 3½-inch diskettes:
DMF in the form of a 1680 kB VFD image and XDF images are supported by Windows Virtual PC.