To fix the “Excel file format and extension don’t match” error, first check if the file extension matches its format. Try renaming the file with the correct extension (e.g., .xlsx for Excel ...

How to open a .csv file in Excel. Opening a .csv file is as easy as opening a .txt file, and usually, you won’t have to clean up the data before doing so because the save task inserts the delimiter.

To change the default file format for saves in Excel, follow these steps-Open Excel on your computer. Click the File option from the top menu bar. Click on the Options button.

Launch Microsoft Excel and then press "Alt-F" to switch to the File tab. Select "Options" from the menu, and then select "Manual" from under Calculation Options on the Formulas tab.

Now Numbers will convert the file into one you can open and use in Excel. That’s it. Now you’re free to pursue a life of spreadsheet happiness and may no file format put asunder.