Convert XLS to XLSX — Free & Private
Fast, free, private. Convert XLS to XLSX without uploading to any server.
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About XLS to XLSX Conversion
Transform your documents for maximum compatibility. Whether you're switching between Office formats, converting to universal PDF, or adapting files for specific software, our converter handles the complexity.
How to Convert XLS to XLSX
Converting files has never been easier or more secure. MixConvert uses advanced browser-based technology to process your files instantly without uploading them to a remote server. Follow these simple steps to get started:
- Select Your Files: Select your XLS files by clicking the upload zone or dragging them directly onto the page.
- Choose Output Format: Confirm XLSX is set as the destination format in the format selector.
- Convert Instantly: Click the convert button to begin. Your XLS files will be processed locally in seconds.
- Download: Save your new XLSX files directly to your device. Batch download available for multiple files.
XLS to XLSX FAQ
Can I convert XLS to XLSX on mobile devices?
Absolutely! Our converter is fully responsive and works on any smartphone or tablet. Just visit this page, upload your XLS files, and convert them to XLSX format—no app required.
Is my data secure when converting XLS files?
100% secure. Unlike cloud converters, MixConvert processes your XLS files entirely on your device using WebAssembly. Your data stays on your computer—we never see it.
How large can my XLS files be?
We don't impose file size restrictions. Your browser handles the conversion, so the limit depends on your device's memory. Typical computers can process very large XLS files without issues.
What's the conversion speed for XLS files?
Conversion is nearly instant for typical XLS files. Your device's processor handles the work, so faster devices complete XLSX conversion more quickly.
Does MixConvert support converting multiple XLS files at once?
Batch conversion is fully supported. Upload as many XLS files as you need and convert them all to XLSX in one go. A ZIP download option makes it easy to save everything.
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Understanding the Formats
XLS
Microsoft Excel 97-2003
Legacy Excel format for compatibility with older systems.
XLSX
Microsoft Excel Workbook
Excel's modern spreadsheet format supporting formulas, charts, and multiple sheets.
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