.xlsx File — Office Open XML Spreadsheet

XLSX is the default spreadsheet format for Microsoft Excel since Office 2007, based on the Office Open XML standard (ECMA-376). Like DOCX, an XLSX file is a ZIP archive containing XML files that describe worksheets, shared strings, styles, formulas, and chart definitions. The format supports up to 1,048,576 rows and 16,384 columns per sheet, dramatically expanding capacity over the legacy XLS format. XLSX supports conditional formatting, sparklines, slicers, pivot tables, data validation, and structured table references. Because the format is XML-based, it offers better interoperability with other software, smaller file sizes through ZIP compression, and improved corruption recovery. The format does not support VBA macros by default — macro-enabled files use the XLSM extension instead. XLSX has become the industry standard for spreadsheet data exchange in business, finance, and data analysis contexts worldwide.