The purpose of MIDI Files is to provide a way of interchanging time-stamped MIDI data between different programs on the same or different computers. One of the primary design goals is compact representation, which makes it very appropriate for a disk-based file format, but which might make it inappropriate for storing in memory for quick access by a sequencer program. (It can be easily converted to a quickly-accessible format on the fly as files are read in or written out.) It is not intended to replace the normal file format of any program, though it could be used for this purpose if desired.

MIDI Files contain one or more MIDI streams, with time information for each event. Song, sequence, and track structures, tempo and time signature information, are all supported. Track names and other descriptive information may be stored with the MIDI data. This format supports multiple tracks and multiple sequences so that if the user of a program which supports multiple tracks intends to move a file to another one, this format can allow that to happen.