What is an XLSX file?
XLSX is the spreadsheet format of Microsoft Excel since 2007. Like DOCX it is a ZIP package of XML parts: one part per worksheet with the cell values and formulas, a shared string table, styles, defined names and charts. Values and formulas are stored separately, so a converter can read results without recalculating.
A worksheet can hold 1,048,576 rows and 16,384 columns. Formulas, conditional formatting, pivot tables, data validation and charts are all part of the standard (ISO/IEC 29500), which LibreOffice Calc and Google Sheets implement to a large extent.
When XLSX is the right choice
Strengths
- Keeps formulas, formatting, multiple sheets and charts in one file
- Readable by Excel, LibreOffice Calc, Google Sheets and Numbers
- Typed cells: numbers, dates and text stay distinct, unlike CSV
Limitations
- Not a plain-text format: scripts and databases prefer CSV for import
- Macros require the XLSM variant; XLSX strips them
- Complex formulas may recalculate differently outside Excel
How to open an XLSX file
Excel, LibreOffice Calc, Google Sheets and Apple Numbers open XLSX directly. To share a read-only view of the sheets with page breaks and headers in place, Excel to PDF produces a document anyone can open.
How to convert an XLSX
Excel to PDF fixes the layout for sharing. Going the other way, PDF to Excel rebuilds tables from a PDF report, and PDF to CSV gives the plain data. Legacy workbooks move to the current format with XLS to XLSX.