You don't remember correctly. Word's docx format is far more intelligent than openoffice ODT, despite propaganda to the contrary. With one exception: word's zip

You don't remember correctly. Word's docx format is far more intelligent than openoffice ODT, despite propaganda to the contrary. With one exception: word's zip files don't have a convenient magic header. The way it works with ODT, and a bunch of other formats is that you put an uncompressed identifier file (`mimetype`) as the first entry inside your zipfile. At byte 30 (of your zipfile) you then get `mimetype$THE_MIMEMETYPE`. This is a nice trick and works for any zip-based format. Sadly, docx does not do that so you have to go by file extension or look at (more of) the contents of the zipfile.