Using Your Own File Extensions

By default, Excel uses either XLSX or XLSM as a filename extension for all workbook files, depending on whether the workbook contains macros or not. If you don’t want to use the default file extensions for a workbook you are saving, you can pick something different. (You may want to use a different extension if you are trying to hide the fact that the file is an Excel workbook.)

If you try to use a different file name extension by including it when you save the file, Excel still appends the XLSX or XLSM extension. For instance, if you explicitly save a file as MyFile.mef, Excel will still save it as MyFile.mef.xlsx.

If you don’t want Excel to do this, then simply enclose your file name in quotes when you save under a new name. Thus, you would use the name “MyFile.mef” (with the quotes) and that is the file name which Excel will use.

In addition, if you save a workbook with a different extension (not one of the defaults used by Excel), then Excel won’t show the workbook by default when you use the Open command. To see all your varied-extension files, you need to follow these steps:

  1. Displays the Open dialog box.
  2. In the File Name field, enter an asterisk, period, and your desired extension. For instance, you could enter “*.mef” (without the quotes).
  3. Press Enter. The desired files should be listed in the directory.
  4. Select the file you want to open.
  5. Click on Open.