The recommended file suffixes for MusicXML files are .mxl for compressed files and .musicxml for uncompressed files. Using unique file suffixes lets programs distinguish MusicXML files from generic XML files in a way that using the .xml suffix for uncompressed files does not.
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 .musicxml files that are contained within the zip archive.
For Internet use, MusicXML 3.1 has registered media types available for both compressed .mxl and uncompressed .musicxml files. The recommended media type for a compressed MusicXML file is:
The recommended media type for an uncompressed MusicXML file is: