XLS to XLSX Converter
Convert Excel Binary Spreadsheet (XLS) to Office Open XML Spreadsheet (XLSX) online for free. Runs 100% in your browser. Files never leave your device. No signup, no watermarks, no limits.
Drag & drop files here, or browse
Processed on your device. Nothing is uploaded
Automate this. An open tab can convert whole folders via the Local API - still zero uploads.
Local API →How to use XLS to XLSX Converter
- 01Add files
Choose files or drop them here
- 02Settings
Settings · Runs on your device
- 03Download
Processed on your device. Nothing is uploaded
What is a XLS (Excel Binary Spreadsheet) file?
XLS is the legacy binary Excel format (1997–2003). Modern pipelines often need it converted to XLSX or CSV first.
- Developed by
- Microsoft
- Initial release
- 1987
What is a XLSX (Office Open XML Spreadsheet) file?
XLSX is the default Microsoft Excel format since Office 2007. Converting XLSX to CSV makes the data usable in scripts, databases and other apps.
- Developed by
- Microsoft
- Initial release
- 2007
Frequently asked questions
How do I convert XLS to XLSX?
Click “Choose Files” or drag your XLS file onto the page, optionally adjust the settings, then hit Convert. Your XLSX file downloads straight from your browser. Nothing is uploaded anywhere.
Is this XLS to XLSX converter free?
Yes, completely free with no hidden limits, watermarks or signup. Because all processing happens on your own device, there are no server costs to pass on to you.
Are my files uploaded to a server?
No. The conversion engine runs entirely in your web browser using WebAssembly. Your files never leave your device. You can even disconnect from the internet after the page loads and keep converting.
Is there a file size limit?
We impose no fixed limit. The practical ceiling is your device's free memory, since processing happens locally. Most conversions work comfortably with files up to a few hundred megabytes, and image or document conversions handle much more.
Does it work on my phone?
Yes. The converter runs in any modern browser on Windows, macOS, Linux, Android and iOS. No app installation is required.