What is the default file extension for a Microsoft Excel workbook?

The default file extension for a Microsoft Excel workbook is .xlsx. This extension was introduced with Excel 2007 and signifies an XML-based file format, offering improved data recovery and smaller file sizes compared to older formats.

• .xls was the default extension for older Excel versions (Excel 97-2003).
• .csv stands for Comma Separated Values, a plain text file format for tabular data, not a native Excel workbook.
• .docx is the default file extension for Microsoft Word documents.