XLSX File Format
XLSX is the default spreadsheet format for Microsoft Excel, based on the Office Open XML standard for tabular data and calculations.
Sample XLSX Files
View all| File Name | Size | Description | Action |
|---|---|---|---|
| Financial Report | 18 KB | Download | |
| Sales Dashboard | 28 KB | Download | |
| Legal Invoice Template | 18 KB | Download |
Overview
XLSX is the default spreadsheet format for Microsoft Excel since 2007. Like DOCX, it is a ZIP archive containing XML files that define worksheets, cell data, formulas, styles, charts, and pivot tables. XLSX supports up to 1,048,576 rows and 16,384 columns per sheet, conditional formatting, data validation, VBA macros (as .xlsm), and Power Query connections. It is the industry standard for financial modeling, data analysis, reporting, and business intelligence.
History
Microsoft introduced XLSX with Office 2007 as part of the Office Open XML transition. The format replaced the binary .xls format (BIFF) that had been used since Excel 97. XLSX was standardized as part of ECMA-376 and ISO/IEC 29500. The XML-based structure improved interoperability with other tools and made spreadsheet data accessible to programmatic processing with libraries like openpyxl, Apache POI, and SheetJS.
File Structure
An XLSX file is a ZIP archive containing: xl/workbook.xml (workbook metadata), xl/worksheets/sheet1.xml (cell data per sheet), xl/sharedStrings.xml (string table for deduplication), xl/styles.xml (formatting), and xl/theme/theme1.xml (visual theme). Formulas are stored as text in cell elements, and charts are stored in xl/charts/. The Open Packaging Conventions define the overall structure.
Common Use Cases
- Financial modeling and budgeting
- Data analysis and reporting
- Inventory and project tracking
- Scientific data collection and tabulation
- Import/export format for databases and ETL
- Pivot tables and dashboards
- Payroll, invoicing, and accounting
- Statistical analysis with formulas
Advantages
- •Powerful formula engine and calculation features
- •Supports charts, pivot tables, and conditional formatting
- •Widely supported across spreadsheet applications
- •XML-based and ZIP-compressed for smaller size
- •ISO standard ensures interoperability
- •Handles over 1 million rows per sheet
Disadvantages
- •Complex format makes programmatic editing non-trivial
- •Formatting can differ between Excel, Sheets, and Calc
- •Macro-enabled .xlsm files can contain malware
- •Large files with formulas can be slow to recalculate
- •Not ideal for streaming or real-time data pipelines
Frequently Asked Questions
What is an XLSX file?
An XLSX file is a Microsoft Excel spreadsheet based on the Office Open XML standard. It stores tabular data, formulas, charts, and formatting in compressed XML files inside a ZIP archive.
How do I open an XLSX file?
XLSX files can be opened with Microsoft Excel, Google Sheets, LibreOffice Calc, Apple Numbers, WPS Office, and many other spreadsheet applications.
What is the difference between XLS and XLSX?
XLS is the legacy binary format (Excel 97-2003) limited to 65,536 rows, while XLSX is the newer XML-based format supporting over 1 million rows. XLSX files are smaller and based on an open standard.
Can I convert XLSX to CSV?
Yes. Open the file in Excel or Google Sheets and Save As/Download as CSV. You can also use command-line tools like csvkit or programming libraries like pandas (Python).