XLS is the primary format for Microsoft Excel. It is the default for saving spreadsheets which hold data like charts and macros. Warning: because of it’s popularity .xls is a file which is often infected when send by people you don’t know. Do not open these files without scanning them first.
Mime type: application/vnd.ms-excel [official], application/msexcel, application/x-msexcel, application/x-ms-excel, application/vnd.ms-excel, application/x-excel, application/x-dos_ms_excel, application/xls