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XLS to XLSX

Upgrade legacy Excel .xls files to the modern .xlsx format. All sheets and data preserved. Runs entirely in your browser.

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Drop an .xls file or browse

Legacy Excel 97–2003 format

What is XLS to XLSX?

XLS to XLSX upgrades legacy Microsoft Excel .xls files (Excel 97–2003 binary format) to the modern .xlsx format (Office Open XML). XLSX files are smaller, more compatible, and supported by all modern apps.

How It Works

Drop your .xls file. SheetJS reads the legacy binary format, preserving all sheets, cell data, formulas, and basic formatting. It then writes the data as a modern .xlsx file — entirely in your browser. Nothing is uploaded.

Key Benefits

  • 100% browser-based — your files never leave your device
  • All sheets, data, and formulas are preserved
  • XLSX is smaller and more compatible than XLS
  • Supported by Excel, LibreOffice, Google Sheets, and all modern apps
  • Free — no account or registration needed

Frequently Asked Questions

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