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XLSX converter

An .xlsx file is a modern Excel workbook — a ZIP archive of SpreadsheetML XML parts describing sheets, shared strings, styles, and formulas. It has been Excel's default save format since 2007 and the de facto interchange format for tabular business data.

Private for supported formats — processed in your browser

Convert supported files

Runs on your device

Drop XLSX files here

Batch files can each use a different output. Nothing uploads for local conversions.

Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.

Where XLSX comes from

The format arrived with Excel 2007 under the Office Open XML umbrella that ECMA-376 codified in 2006, with ISO/IEC 29500 adoption two years later. It multiplied BIFF's grid limits enormously and pushed macros out into the separate .xlsm variant.

How XLSX works

  • xl/worksheets/sheetN.xml holds rows of typed cells; text cells usually point into xl/sharedStrings.xml to avoid repetition.
  • The grid allows 1,048,576 rows by 16,384 columns per sheet.
  • Dates are stored as serial numbers plus a display format — including the deliberate 1900 leap-year bug kept for Lotus 1-2-3 compatibility.
  • Formulas are saved as text alongside the last cached result, so readers can show values without recalculating.
  • ZIP packaging permits partial reads: one sheet can be pulled out without decompressing the rest.

When to use XLSX

  • The standard vehicle for exchanging spreadsheets between organizations.
  • Data exports destined for analysis in pandas, R, or BI tools.
  • Financial models and budgets with live formulas.
  • Bulk data entry templates for web application imports.

Strengths and limitations

Strengths

  • Vast grid limits compared with the legacy .xls format.
  • Documented ZIP-of-XML anatomy — any ZIP and XML library can mine it, which is how in-browser conversion works here.
  • Cached formula results let lightweight readers display correct values.
  • Macros are excluded by design, so .xlsx is safer to open than .xlsm.

Limitations

  • Date-as-serial-number storage causes subtle off-by-one and timezone bugs.
  • XML verbosity makes very large workbooks slower than the binary .xlsb alternative.
  • Styling and chart fidelity vary across non-Microsoft implementations.

Compatibility

Excel 2007 onward, LibreOffice Calc, Google Sheets, and Apple Numbers all handle .xlsx, and nearly every data-processing library reads it. Support is equally solid on iOS and Android through the same vendors' apps.

docProps/core.xml carries Dublin Core creator and date fields while docProps/app.xml records the generating application and company — both ride inside the ZIP.

Convert XLSX to another format

Convert other formats to XLSX