Regular, plain text MusicXML files can be very large – much larger than the original Finale and Sibelius files, or corresponding MIDI files. This was not a big problem for using MusicXML as an interchange format, but it inhibited MusicXML’s use as a sheet music distribution format.
MusicXML 2.0 introduced a new compressed format which reduces MusicXML file sizes to roughly the same size as the corresponding MIDI files. The format uses zip compression and a special .mxl file suffix and Internet media type to identify files as MusicXML files vs. generic XML files. This section describes how the compressed format works.