Key facts
- MIME type application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.
- A ZIP archive of XML parts: xl/workbook.xml, one xl/worksheets/sheetN.xml per sheet and xl/sharedStrings.xml for text.
- Each sheet holds up to 1,048,576 rows by 16,384 columns (A to XFD).
- .xlsm is the macro-enabled variant and .xlsb a binary variant; plain .xlsx cannot store VBA macros.
How to open a .xlsx file
Windows
Open it in Excel, free in Excel for the web, or in LibreOffice Calc. Power Query (Data > Get Data) can import sheets into other workbooks.
macOS
Open it in Numbers (free), Excel for Mac or LibreOffice Calc. Quick Look previews the sheets.
Linux
Use LibreOffice Calc, or convert in the terminal with libreoffice --headless --convert-to csv data.xlsx (first sheet). Python's openpyxl or pandas read it programmatically.
Common problems and fixes
- 'We found a problem with some content' when opening
- Click Yes to let Excel repair it and review the repair log, or use File > Open > Open and Repair. If that fails, try LibreOffice, which tolerates many XML errors.
- File is corrupt or 0 bytes after download
- The ZIP container is truncated. Test it with unzip -t data.xlsx; re-download or restore a previous version from OneDrive or File History if entries are broken.
- Accents and non-English text break when exported to CSV
- Choose 'CSV UTF-8 (Comma delimited)' instead of plain CSV when saving, or fix the encoding of the exported file afterwards.
- Leading zeros, long IDs or dates change
- Excel auto-converts values that look like numbers or dates. Format those columns as Text before entering or importing data, or import CSVs via Data > From Text/CSV with column types set.
Often converted to or from: CSV, XLS, ODS, PDF, JSON