Convert XLS to XLSX Online
Convert Excel to Excel without installing software. The conversion runs on the server in an isolated request. The tool is free, handles batches, and accepts server files up to 100 MB each. Keep the original file while you review the converted copy.
Convert .XLS to .XLSX
Select a file to begin. Processing details and limits are listed below.
How to convert XLS to XLSX
- 1
Upload Excel files
Add one or more Excel files to the queue. The uploader keeps batch items separate.
- 2
Choose Excel settings
Set the available quality or format options, or keep the defaults for a first pass.
- 3
Create the Excel file
Run the queue and download the Excel files individually or together as a ZIP.
Legacy Excel Spreadsheet vs Microsoft Excel Spreadsheet
| Spec | Legacy Excel Spreadsheet | Microsoft Excel Spreadsheet |
|---|---|---|
| MIME type | application/vnd.ms-excel | application/vnd.openxmlformats-officedocument.spreadsheetml.sheet |
| Format type | data | data |
| Contents | Binary Excel 97-2003 format. | Structured spreadsheet with formulas. |
About Legacy Excel Spreadsheet
Binary Excel 97-2003 format.
About Microsoft Excel Spreadsheet
Structured spreadsheet with formulas.
Why convert XLS to XLSX?
- A converted copy keeps the original file intact for comparison and future edits.
- The output can be tested in the destination workflow before the original is archived.
- A separate copy makes it easier to compare the old and new behavior.
- Conversion is useful when the destination has a strict format requirement.
Will quality change?
Office and PDF engines interpret layout differently. Check headers, footers, images, and tables after conversion. Review the file in the application where it will be used.
Processing and limits
- Processing
- Server-side
- Engine
- LibreOffice and document tooling
- Maximum size
- 100 MB per file on the server.
- Batch support
- Yes, multiple files can be queued; completed results can be downloaded as a ZIP.
- Quality controls
- No quality slider. The output follows the fixed conversion path.
The file is processed on the server because the conversion requires a server-side engine or a utility operation.
- Excel features without a direct Excel equivalent may not survive the conversion.
- Conversion cannot restore detail that the source format already discarded.
- Complex, encrypted, or unusually structured files may need manual review.
Platform compatibility
The output is a Excel file. Use an application or device that accepts that format, and test the result on the destination platform if compatibility is critical.
When not to convert
- If Excel support is uncertain on the destination device, test a sample before processing a large batch.
- Do not use a converted file as the legal or signed original when signatures or metadata must be preserved.
- Do not overwrite the source; keep both versions until the output has been approved.
Frequently asked questions
- How do I convert Excel to Excel online?
- Upload a Excel file, choose the available Excel options, run the conversion, and download the result. The tool is free, supports batches, and accepts server uploads up to 100 MB.
- Is Convert XLS to XLSX free?
- It is free, requires no account, and adds no watermark. Server uploads are limited to 100 MB per file, and browser-first paths are limited by device memory.
- What happens to quality?
- Office and PDF engines interpret layout differently. Check headers, footers, images, and tables after conversion. Review the file in the application where it will be used.
- Does the file leave my device?
- Yes. This conversion uses a server-side engine, so the file is uploaded over HTTPS, processed in an isolated request, and removed after the result is produced.
- Is batch conversion supported?
- Queue multiple files, run them together, and download the finished results as a ZIP. Each server file is limited to 100 MB, and large batches may take longer.
- What are the limitations?
- Open the downloaded Excel file in the application or database you plan to use, check the structure against the source, and keep the original until the output is approved.