Understanding Excel file extensions and their uses is critical when exchanging or sharing data with colleagues, clients, or partners. Excel offers a wide range of file formats that serve specific ...

If your Excel files are opening in Notepad on Windows PC, here's how you can reset the settings to make .xls, .xlsx, etc files open in Excel.

With the Excel extension is not valid error, try starting the app in Safe Mode, repair the workbook or open the file in another program.

One common challenge that users face is encountering the error message Excel cannot open the file because the file format or file extension is not valid .

If your Excel files are opening in Notepad, you should be able to open it by changing the default file types settings, among other fixes.