The recommended file suffix for compressed MusicXML files is .mxl. Using a unique file suffix lets programs distinguish MusicXML files from generic XML files in a way that using the .xml suffix for uncompressed files does not. As an example, Myriad’s QuickLook plug-in for Mac OS 10.5 relies on the .mxl suffix to indicate that it should provide a preview of the score image in the Mac Finder application.
Many XML editing tools such as XMLSpy and Oxygen now support the editing of zip-compressed XML files. All that is necessary is to let the editor application know that .mxl files are a zip-based format. The editor will then let you edit both the structure of the .mxl file as well as the .xml files that are contained within the zip archive.
For Internet use, MusicXML 3.0 has registered media types available for both compressed .mxl and uncompressed .xml files. The recommended media type for a compressed MusicXML file is:
The recommended media type for an uncompressed MusicXML file is: