What file format is best for saving an Excel workbook that contains macros?

The best file format for saving an Excel workbook that contains macros is .xlsm. This format specifically allows for the storage of macros that are created using Visual Basic for Applications (VBA) within Excel. When you save a workbook as .xlsm, it retains the functionality of the macros, ensuring they can be executed when the workbook is reopened.

The .xls format is an older version that also supports macros, but it is less commonly used in modern versions of Excel. It has limitations related to features and size compared to .xlsm. The .xlsx format, on the other hand, does not support macros at all, so any macros would be lost if saved in this format. Lastly, the .xlsb format is a binary format that can also store macros, but it is typically used for performance reasons or to reduce file size rather than specifically for macro functionality. Therefore, while .xlsb is a viable format for macro-enabled workbooks, .xlsm is the standard and most straightforward choice for general use.