File Types in Microsoft Excel 2007 or Later

Starting with version 2007, Microsoft Excel supports three main new XML-based file formats:

XLSX—Office Open XML format without support for VBA or macros
XLSM—Office Open XML format including support for VBA or macros
XLSB—Office Open binary format (in an XML structure that contains binary data instead of XML data)

By default, any new workbooks created in Microsoft Excel 2007 or later are created in one of these file formats.

You can also open older Microsoft Excel 97-2003 workbooks with file extension XLS in Microsoft Excel 2007 or later. These older workbooks are opened in a special compatibility mode (identified by “[Compatibility Mode]” after the filename in the window title) so you can operate on them in much the same manner as with newer file formats. You cannot, however, use any of the new Microsoft Excel 2007 or later features such as the expanded grid size, new chart types, and so on.

You can use the Save As command in Microsoft Excel 2007 or later to convert your older XLS files to one of the new file formats or, optionally, to convert the new formats to XLS.