DOC and DOCX are standard file formats of the widely used Microsoft application Word.

The binary DOC is the original file format of this software and was directly developed by Microsoft.

Office Open XML DOCX has been the successor of DOC since Word 2007. This is a completely different file format. In fact, it is a ZIP compression file that contains XML files and any additions such as images.

The development of DOCX has a rich history. Three implementations of the format have emerged: the now outdated versions ‘ECMA’ and‚ ‘Transitional’ and the current open standard ‘Strict’. Older versions of Word are not able to store DOCX in “Strict”, for a long time transition format “Transitional” has seen more use and this implementation still occurs. This can lead to problems with the format support.
In addition, use can be made of internal Microsoft standards that are not public.
For these reasons, DOCX is provisionally seen as a non-preferred file format.

Microsoft Word (.doc) and Office Open XML (.docx) are non-preferred formats for file type Text documents.