What is the default file format for an Excel Workbook in Excel 2016 and later versions?

The default file format for an Excel Workbook in Excel 2016 and later versions is .xlsx. This format was introduced in Excel 2007 and is designed to store data in a more efficient and stable manner than the older .xls format. The .xlsx format benefits from reduced file sizes and improved data recovery options, making it the preferred choice for users.

Using .xlsx allows for a wide range of features, including support for tables, charts, and various data analysis tools, all of which enhance the user experience. Additionally, .xlsx files do not contain the macro capabilities found in .xlsm files, which are specifically for workbooks with macro-enabled content. The .csv format, on the other hand, is used for plain text data and isn't suited for the rich features available in Excel workbooks. Thus, .xlsx is clearly the most suitable and standard format for general use in Excel 2016 and beyond.