What is the file extension for Microsoft's Word document format?

The file extension for Microsoft's Word document format that is currently recognized and widely used is .docx. This format was introduced with Microsoft Word 2007 and continues to be the standard for Word documents. The .docx extension signifies an XML-based file format that allows for smaller file sizes and improved data recovery compared to the older .doc format, which was used prior to Word 2007. As a result, while .doc was the older format, .docx is now the preferred and more common extension for Word documents.

In contrast, .txt is a plain text file format that does not support formatting or rich content, .doc was used in earlier versions of Word but has been largely replaced by .docx, and .pdf is a format designed for documents that need to be shared and printed while preserving the formatting, typically used for non-editable files. Thus, while .doc is associated with Microsoft Word, it is not the current standard format.