For earlier versions of Excel like Excel 2003 a compatibility pack could be downloaded from the Microsoft home page, but this option is no longer officially available. Likewise, the manufacturer of the free Excel Viewer tool, which up to now was used by many users to open the new format, does not offer it officially either. It is no longer possible to open and work with the new format in older versions of Excel.
However, it is not necessary to purchase a new version of Excel to open an XLSX file. There are free alternatives : Microsoft itself offers Excel online as a solution that can be used directly in the browser. You only need a user account for this. Also third-party programs can work with XLSX files. For example, the free source program LibreOffice is compatible with current Microsoft extensions. However, it could be the case that the content (especially as regards the format) does not correspond exactly to the original.
In contrast, in all new versions of Excel it is still possible to save a file in the old XLS format . For this you must use the option? Save as? and, in? Book file type ?, select the option? Excel 97-2003 book (* .xls) ?. In this way, all Excel versions since 1997 can open this file. However, some functions in the XLSX file may no longer be available in the XLS file or the format appears changed. Therefore, it is recommended to use this option only if it is known that the recipient of the file does not have a current version of Excel.