Excel File Extensions: XLSX, XLSM, XLS, XLTX, and XLTM - Lifewire
https://www.lifewire.com/excel-file-extensions-and-their-uses-3124113
WebMay 28, 2020 · Excel uses a handful of standard extensions to disambiguate certain kinds of spreadsheet files. The information in this article applies to Excel 2019, Excel 2016, Excel 2013, Excel 2010, Excel 2007, Excel Online, and Excel for Mac.
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