XLSX file format: what it is and how to use it

XLSX is the Excel workbook: Office Open XML spreadsheets with formulas, styles and multiple sheets that run the world's data work. Learn when to use it and what to choose instead.

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What is a XLSX file?

An .xlsx file is a workbook in Excel's Office Open XML format, a ZIP of XML parts holding sheets, cells, formulas, styles, charts and tables, standardized as ISO/IEC 29500 and native to Excel since 2007. It is the file the world's data work actually happens in, from expense reports to datasets with millions of rows.

When should you use XLSX?

  • Real spreadsheet work: formulas, styles, multiple sheets, charts and pivots.
  • Data exchange within business: the format colleagues and tools expect.
  • Structured tables: typed cells, not just text, numbers stay numbers.

When is another format a better fit?

For pure data interchange between systems, CSV is simpler and universal. For open-standard shops ODS; for sharing a finished view PDF. And for actual databases, use a database, because XLSX is a spreadsheet, not storage.

The short version: XLSX is the world's working table. Build spreadsheets in it, and export CSV or PDF when the data travels.

How to open a XLSX file

On Windows

Double-click the file, or open it with Microsoft Excel.

On macOS

LibreOffice Calc opens XLSX files on macOS.

In your browser

Open XLSX files right in a browser tab or with the dexrr viewer. No install, no upload.

Also opens in

  • Microsoft Excel
  • LibreOffice Calc
  • Google Sheets
  • OnlyOffice

View or convert XLSX files

A quick preview or a new format. No install, no upload.

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XLSX technical details

Full name
Office Open XML spreadsheet
Extensions
.xlsx
MIME type
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
Magic bytes
50 4B 03 04 (ZIP container)
Compression
Lossless
Developer
Microsoft (ECMA-376 / ISO 29500)
Specification
ecma-international.org

XLSX questions, answered

How do I open a .xlsx file?

Excel, Google Sheets, LibreOffice Calc and Numbers open it. dexrr displays and converts xlsx files directly in your browser.

Can I convert XLSX files online?

Yes, dexrr converts xlsx locally in your browser: XLSX to CSV for data, XLSX to PDF for reports or XLSX to ODS for open-standard suites.

Is XLSX better than CSV?

For working data, absolutely: types, formulas, multiple sheets. For moving data between systems, CSV is the simpler universal format.

Why did my CSV export lose the formulas?

CSV stores only current values, one sheet, no formatting. That is the format, not a bug. Keep the .xlsx as the working file.

Is the XLSX format outdated?

No, it is the entrenched standard for spreadsheets across business, science and government.