XLSX File Format (Microsoft Excel Open XML Spreadsheet)
XLSX is the default spreadsheet format for Microsoft Excel, introduced with Office 2007 as part of the Office Open XML (OOXML) standard. Like DOCX, XLSX files are ZIP archives containing XML files that define worksheets, cell data, formulas, formatting, charts, and pivot tables. XLSX is the dominant spreadsheet format in business, finance, science, and data analysis. The format supports up to 1,048,576 rows and 16,384 columns per worksheet, with features including conditional formatting, data validation, macros (in .xlsm), and advanced charting. XLSX is supported by Microsoft Excel, Google Sheets, LibreOffice Calc, and Apple Numbers.
Quick Facts
- Extension: .xlsx
- MIME Type: application/vnd.openxmlformats-officedocument.spreadsheetml.document
- Category: document
Advantages
- Industry-standard spreadsheet format for data analysis
- Supports complex formulas, charts, and pivot tables
- Large capacity (1M+ rows, 16K columns)
- Cross-platform support (Excel, Google Sheets, LibreOffice)
- Rich formatting and data visualization options
Disadvantages
- Complex files can be slow to open and process
- Not suitable for simple data exchange (CSV is simpler)
- Formulas can break when opened in non-Excel applications
- Macro-enabled .xlsm files pose security risks
- Large XLSX files with many formulas consume significant memory
Common Use Cases
- Financial modeling and budgeting
- Business data analysis and reporting
- Inventory management and tracking
- Scientific data collection and analysis
- Project planning and scheduling
Technical Details
XLSX uses SpreadsheetML within the OOXML package. Worksheet data is stored in xl/worksheets/sheet1.xml etc., with shared strings in xl/sharedStrings.xml (to avoid repeating string values), styles in xl/styles.xml, and workbook-level data in xl/workbook.xml. Cell references use A1 notation. Formulas are stored as text strings with a calculated cache value. The calcChain.xml file determines formula recalculation order. Charts use DrawingML within the package. Conditional formatting, data validation, and auto-filters are defined per-worksheet.
Frequently Asked Questions about XLSX
What is the difference between XLS and XLSX?
XLS is the legacy binary format (Excel 97-2003) limited to 65,536 rows. XLSX is the modern XML-based format supporting 1M+ rows. XLSX files are typically smaller and more reliable.
Can I open XLSX without Excel?
Yes. Google Sheets, LibreOffice Calc, and Apple Numbers all open XLSX files. Google Sheets can import directly from Drive or upload.
How do I convert XLSX to CSV?
FileChange converts XLSX to CSV in your browser. Each worksheet can be exported as a separate CSV file with comma-separated values.
Why are XLSX files sometimes corrupted?
Corruption occurs from interrupted saves, storage issues, or software bugs. XLSX ZIP structure makes partial recovery possible by extracting readable XML content.