The file extension XLSX is the default file extension used by Microsoft Excel 2007 and later. Excel is used to create spreadsheets for saving tabular data (such as membership rosters) and for performing financial calculations (such as monthly budgets).
Microsoft first introduced XLSX files with the launch of Microsoft Office 2007.
XLSX files are automatically compressed, which means they're up to 75 percent smaller than XLS files that contain the same data. The structure of XLSX files also means they are less prone to file corruption.
XLS files, the predecessors to XLSX files, could contain macros (automatic scripts), but you could never tell just from looking at the file. However, XLSX files can never contain macros; Excel files with macros are saved with the XLSM extension.
The last X in the file extension XLSX stands for XML (extensible markup language). The XML format is an open standard that is royalty- and license-free. Many other programs also use XML, which means XLSX files can be opened and edited by more applications.
Versions of Microsoft Excel prior to 2007 cannot automatically open XLSX files. In order to open these files in Microsoft Excel 2003 and earlier, you need to install Microsoft Office Service Pack 3.
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