Former Lifewire writer Ted French is a Microsoft Certified Professional who teaches and writes about spreadsheets and spreadsheet programs.

A file extension is the group of letters that appear after the last period in a file name.

File extensions are usually 2 to 4 characters long, although they can be of any length.

Excel uses a handful of standard extensions to disambiguate certain kinds of spreadsheet files.

The current default file extension for an Excel file is XLSX.

The main difference between the two is that XLSX is an XML-based open file format and XLS is a proprietary Microsoft format.

But, the newer versions of Excel save and open XLS files for the sake of compatibility with earlier versions of the program.

Excel Backstage View Code That Could

Macros contain code that could damage files and compromise computer security if they come from untrusted sources.

Excel files containing VBA and XLM macros use the XLSM extension.

If an Excel file has either an XLTX or an XLTM extension, it is saved as a template file.

Templates contain saved settings such as the default number of sheets per workbook, formatting, formulas, graphics, and custom toolbars.

However, for the sake of compatibility with the Windows version of the program, Excel for Mac uses the XLSX file extension.

Excel files created in one operating system can be opened the other.

One exception to this is Excel 2008 for the Mac, which does not support VBA macros.

As a result, it cannot open XLMX or XMLT files created by Windows or later Mac versions that support VBA macros.

To change an Excel format (and its extension), follow these steps.

In the dialog box, accept the suggested file name or type a new name for the workbook.

In the Save as type or File Format list, choose the format for the resulting file.

Select Save to save the file in the new format and return to the current worksheet.

Excel For Mac Backstage View