CSV to XLS Converter
Convert CSV files to the legacy Excel .xls (97-2003) format — free and private in your browser.
Convert CSV files to .xls, the binary workbook format used by Excel 97 through 2003. The only reason to choose .xls today is a receiving system that cannot open .xlsx: legacy ERP and accounting software, old lab instruments, or upload forms that validate on the .xls extension.
The output is a genuine BIFF workbook, not a CSV with its extension renamed, so strict legacy importers that sniff the file header accept it. Note the format’s hard limits, which this tool inherits: 65,536 rows and 256 columns per sheet.
If nothing forces you onto the legacy format, prefer the CSV to XLSX Converter — or use the CSV to Excel Converter linked below to pick either format at download time.
Drop your file here or browse from your device
Accepts CSV, TSV, TXT. Up to 20 files; combined maximum: 10 MiB. Files above this hard limit are rejected before local processing.
Tip: select multiple CSV files to combine them into one workbook, one sheet per file.
How to Convert
- Upload one or more CSV files, or paste your CSV data
- Preview the data and adjust formatting options
- Click Convert to generate the .xls workbook
- Download your Excel file
Features
- Outputs legacy .xls (Excel 97-2003) workbooks
- Combine multiple CSV files into one workbook, one sheet per file
- Auto-fit column widths for readable output
- Auto-detects the delimiter (comma, semicolon, tab)
- Runs entirely in your browser — files never leave your device
Use Cases
- Produce a .xls file for Excel 97-2003 or older software
- Send a legacy-format spreadsheet to a system that cannot read .xlsx
- Open CSV data in an older version of Excel with proper columns
Frequently Asked Questions
When should I use .xls instead of .xlsx?
Use .xls only when you need to open the file in Excel 97-2003 or an older application that cannot read the modern .xlsx format. Otherwise .xlsx is recommended — try our CSV to XLSX converter.
Will the .xls file open in modern Excel?
Yes. Modern versions of Excel, Google Sheets, and LibreOffice all still open .xls files.
Can I combine multiple CSVs into one .xls workbook?
Yes. Select several CSV files and each becomes its own sheet in a single .xls workbook.
Is my data uploaded anywhere?
Never. The conversion runs locally in your browser, so your data stays private and works offline.
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