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How to Convert XLS to XLSX Online Free (Step-by-Step)

·5 min read

Legacy .xls files from Excel 97–2003 are still common in government offices, accounting firms, and older database exports. Converting them to .xlsx unlocks modern features and dramatically reduces file size.

How to Convert XLS to XLSX on AllFormat

  1. Open the AllFormat XLS to XLSX converter in any browser.
  2. Upload your .xls file by dragging it into the drop zone.
  3. The tool automatically processes and converts the file.
  4. Download your new .xlsx file immediately.
Convert XLS to XLSX now →

Frequently asked questions

Do I need Microsoft Excel installed to convert XLS to XLSX?

No. AllFormat converts XLS to XLSX entirely in your browser using client-side processing. No software installation is needed.

Will my formulas and cell formatting be preserved?

Yes. The conversion engine maps all BIFF structures to their OOXML equivalents, preserving formulas, conditional formatting, merged cells, and number formats.

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