XLSX (.xlsx)
Microsoft Excel's Open XML spreadsheet format — the standard for numerical data, tables, and calculations.
- Extension
- .xlsx
- MIME Type
- application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
Last updated
What Is an XLSX File?
XLSX is the default format for Microsoft Excel spreadsheets since Office 2007. Like DOCX, it is a ZIP archive containing multiple XML files. The extension stands for Excel Open XML Spreadsheet.
XLSX Internal Structure
Rename any XLSX to .zip and open it:
xl/workbook.xml— list of sheets and their namesxl/worksheets/sheet1.xml— cell data for the first sheetxl/sharedStrings.xml— all text strings (deduplicated)xl/styles.xml— cell formatting definitionsxl/calcChain.xml— formula calculation orderxl/drawings/— charts and images embedded in sheets
Common XLSX Errors
| Error | Cause | Fix |
|---|---|---|
| "Excel cannot open the file because the format is not valid" | Corrupted ZIP structure | Try opening in LibreOffice Calc; re-download if from external source |
| "We found a problem with some content" | Damaged XML inside the XLSX | Click Yes to repair; some data may be recovered |
| Formulas show as text | Automatic calculation disabled | Formulas tab → Calculation Options → Automatic |
| Charts missing | Embedded drawing relationship broken | Recreate charts from the data |
| File opens in Protected View | Downloaded from internet | Enable editing — this is a security feature, not corruption |
XLSX vs CSV
| Factor | XLSX | CSV |
|---|---|---|
| Formulas | Yes | No |
| Multiple sheets | Yes | No (one per file) |
| Formatting | Yes | No |
| Charts | Yes | No |
| Universal compatibility | Requires Excel/Calc | Opens in any text editor |
| File size | Larger | Much smaller |
Use CSV for data exchange between systems. Use XLSX when formatting, formulas, or multiple sheets are needed.