The extension name of MS Word 2010 is .docx. This is the default XML-based file format for Word 2010 and is used by Word 2007 and later versions for Windows, as well as Word 2008 and later versions for macOS. The .docx extension is used for standard Word 2007 or 2010 documents with no macros or code. Other file extensions used by Word 2010 include:

• .dotx: A Word template with no macros or code.
• .docm: A Word document that could contain macros or code.
• .dotm: A Word template that could contain macros or code.

It is important to note that a document with the .docx file extension isnt necessarily a Word 2010 document; it may also be a Word 2007 document as that is the extension used by that release of Word.