XLSX is the default format used by Microsoft Excel, versions 2007 and above. Microsoft Excel is compatible with multiple operating systems and it's currently one of the top applications for creating and editing spreadsheets.
The XLSX format stores data in worksheets. Each worksheet has a grid of cells arranged in columns and rows. Cells can contain text and numbers of various fonts, colors and sizes. XLSX files may also include charts, pivot tables, graphs and mathematical functions. Microsoft Excel also features the Visual Basic macro programming language for applications.
XLSX files are based on the Open XML format which stores all content in a zipped archive. The archive contains XML, RELS and media files (if applicable) stored in three separate folders named “docProps”, “xl” and "_rels". Files with the RELS extension dictate how the parts of the document connect to form a single file. The archive also includes a [Content_Types].xml file which describes the spreadsheet and separate XML files for each worksheet. This archived approach makes file content more accessible. For example images and text are stored individually within the archive.
How to open XLSX files
The contents of an XLSX file can be extracted individually by opening it with a data compression application (i.e. WinZip or WinRAR). The XML files of an XLSX document can be opened with any basic text editor and any web browser.
XLSX files can be opened with a large number of applications including online word processors.