The file extension XLSX is the latest version of the Microsoft Excel xls file format. The XLSX format will be supported starting with the 2007 version of the spreadsheet program used worldwide. The file extension XLSX means Excel Spreadsheet Xml, Excel spreadsheet in XML format.
An XLSX file contains formatting instructions, formulas and graphics in addition to the table cell values, but no macros. Files containing macros are automatically given the extension xlsm.
XLSX is an XML based file format (Office Open XML) that is not legible with older versions of Excel. For the Office versions 2000, 2003 and XP, however, this functionality can be upgraded using the Microsoft Office Compatibility Pack, whereby the result of a read-in XLSX file does not always have to be 100% identical to the original.
Office Open XML is an open standard developed by Microsoft for office applications, which is intended to ensure the file exchange between different office suites.
An XLSX file consists of several XML files, which are automatically summarized as archives when saved using the ZIP algorithm. This saves space compared to the old format. Other benefits include better data integrity and easier data recovery in the event of data loss.