What is the default file extension for a Word document?

The default file extension for a Word document is .docx. This format was introduced with Microsoft Word 2007, replacing the older .doc format. The .docx extension indicates that the file is a Microsoft Word Open XML Document, which allows for easier data recovery and better performance.

This format supports advanced features such as text, images, tables, and formatting while being more efficient in file size compared to its predecessor. When you create a new document in a modern version of Microsoft Word and save it, it will automatically use the .docx extension unless another format is specified by the user. The other extensions mentioned are associated with different applications: .xls is for Excel spreadsheets, .pptx is for PowerPoint presentations, and .txt is for plain text files.