Document format
What is a XLSX file?
XLSX is Microsoft Excel's spreadsheet format, storing formulas, formatting, and multiple sheets of tabular data.
Like DOCX, XLSX arrived with Office 2007 as part of Microsoft's move to the XML-based Office Open XML format, replacing the older binary .xls format. Underneath, it's a zipped bundle of XML files describing every cell, formula, chart, and formatting rule across every sheet in the workbook — open enough that other spreadsheet software (Google Sheets, LibreOffice Calc) can read and write it with a high degree of fidelity, which is a big part of why it became the de facto standard for tabular data exchange, not just within Excel itself.
How to open a XLSX file
XLSX files open readily in Microsoft Excel, Google Sheets, Apple Numbers. For real editing rather than just viewing, reach for Microsoft Excel, LibreOffice Calc (free).
Strengths & limitations
Good for
- live formulas and calculations
- the standard format for spreadsheets
Watch out for
- not a fixed-layout format — printing consistently needs care
Convert XLSX files
Orbfile can convert XLSX both ways, entirely in your browser — pick a direction below:
Frequently asked questions
What does a XLSX file contain?+
XLSX is Microsoft Excel's spreadsheet format, storing formulas, formatting, and multiple sheets of tabular data.
Can I convert XLSX for free?+
Yes — Orbfile's document converter handles XLSX for free, with no file limit, watermark, or account, and it runs entirely in your browser.
Is converting a XLSX file safe and private?+
Yes. Orbfile processes XLSX files locally on your device using WebAssembly — nothing is uploaded to a server, so there's nothing to leak or store.
Who created the XLSX format?+
XLSX was developed by Microsoft, first released around 2007.
Browse the full file format guide.