XM is the extension of files used by the older music composition program FastTracker 2. XM files contained composition designs made in the program. Functionally, they were similar to MOD files, but they gave more possibilities (e.g. they allowed to assign different samples to individual notes and could contain a larger number of patterns). These files were based on the MIDI format.

Fast Tracker 2 was problematic and its successor, Fast Tracker III, was only released in Beta. The XM format itself was supported by other programs. Currently, the format is not being developed.