What is a .xlsx file?

About the format

An .xlsx file is an Excel workbook in the Office Open XML format — like .docx, a ZIP of XML parts under the hood. It holds worksheets, formulas, charts, pivot tables and formatting, and opens in Excel, LibreOffice Calc, Google Sheets and Excel's free web version (heavy workbooks with elaborate formulas or Power Query connections are where compatibility frays). The macro rule is the same as Word's and worth internalising: a plain .xlsx CANNOT contain macros — macro-enabled workbooks are .xlsm (and the old binary .xls can embed anything), so an emailed 'spreadsheet' that arrives as .xlsm or demands 'Enable Content'/'Enable Editing' to show its data is following the exact playbook of Office-macro malware. Excel has also been a data-integrity hazard in its own right — its silent conversion of anything gene-name-or-date-shaped is infamous — so when an .xlsx is the handoff format for important data, check the columns that look like dates, long numbers or leading-zero codes survived intact.

How to open a .xlsx file

Is a .xlsx file dangerous?

Plain .xlsx can't run macros; .xlsm and 'Enable Content' prompts are the risk pattern.

Related file types