This week I was asked “Today I was asked to open, update and resave an XLSB file. I’ve only worked with XLS and XLSX files before. What does this extension with the B mean and what’s the difference between XLSX and XLSB?”

XLSB is a binary file format (the B stands for Binary). The main advantage of a binary file is that the file size is generally smaller than an XLSX file and therefore binary files tend to open and save much faster than XLS or XLSX files.


The main limitation of binary file format is that they cannot be read by other software. Many databases and bespoke systems (and even something like your online bank) have an option to export data as Excel but usually only support XLSX or XLS (the older format for standard Excel files).

Despite what some people say, binary files can store macros or VBA inside them.

Once the file is opened in Excel, the functionality of XLSB and XLSX files is identical.

To open an XLSB in Excel, simply double click the file from Windows Explorer/Finder. Or if you are already in Excel, change the file type dropdown (it’s labelled Enable in 2011 for Mac) in the Open dialog box so that all files are displayed.

To save an XLSB in Excel, simply change the file type dropdown (format dropdown in Excel 2011 for Mac) in the Save dialog box.