If you're still saving Excel spreadsheets with a three-letter .xls extension, you're lugging around a digital anchor from the era of dial-up. Beyond being a 1990s relic, these legacy files are slow, ...

XLS files are Excel workbook files created in Excel 97 or Excel 2003. The 2007, 2010 and 2013 versions of the program use the XLSX format by default to save workbooks, but can also use the XLS format.

If Microsoft Excel fails to recognize a file in the XLSX or XLS format, the data contained in the file could be corrupted. When you open a corrupted workbook in Excel, the program should automatically ...

Microsoft Excel has several features designed to help you recover unsaved versions of spreadsheets and prevent data loss. If Excel closes before you save a file, you should see a Document Recovery tab ...