Why convert XLS to CSV?
- Import legacy data — move old exports into databases and modern tools.
- Automation — CSV is easy to process with scripts.
- Long-term archiving — plain text never needs special software.
How the conversion works
The XLS workbook is read with SheetJS, and each selected sheet is written as CSV using the values shown in Excel, with dates in ISO format.
What is an XLS file?
XLS is the binary workbook format used by Microsoft Excel 97 to 2003. It stores sheets, values and formulas in a compound “BIFF” file rather than the XML used by XLSX. Many older reports, bank exports and archived spreadsheets still use it.
Modern Excel opens XLS files in compatibility mode, but some newer tools and websites no longer accept them, which is why converting XLS to XLSX or CSV is common.
What is a CSV file?
CSV (comma-separated values) stores a single table as plain text: one row per line, with cells separated by commas (or semicolons or tabs in some regions). Cells that contain commas, quotes or line breaks are wrapped in double quotes.
CSV is the universal exchange format for data — almost every database, spreadsheet, CRM, bank and analytics tool can import and export it. It has no formatting, formulas or multiple sheets, and it does not record its own text encoding, which is why non-English CSV files sometimes open with garbled characters.