Microsoft Word Document

.docx is a Microsoft Word Document. The modern XML-based Word document format (Office 2007 and later), stored as a zipped package.

.docx files open with: Microsoft Word, LibreOffice Writer, Google Docs.

The MIME type of .docx is "application/vnd.openxmlformats-officedocument.wordprocessingml.document" — the identifier browsers and servers use for this format.