A file extension for the latest MS Excel spreadsheet format which is based on the Open XML data format. The XLSX format was introduced with MS Excel 2007. XLSX files are ZIP-compressed for smaller size. Version 2007 of the MS Office suite has extended its support for the Open XML data specification by adopting an XML-based format for Excel 2007, Word 2007 and PowerPoint 2007. This file format is known as Office Open XML; it has been created to address some issues that users face when creating portable MS Office documents.