CSV ↔ XLSX Converter
Drop a .csv file to get an Excel .xlsx workbook, or drop a .xlsx/.xls file to get a plain .csv — direction is detected automatically. Runs entirely in your browser; nothing is uploaded to a server.
Click to upload or drag and drop
CSV, XLSX, or XLS
How direction is chosen
The tool looks at the file you drop: a .csv file converts to .xlsx, while a .xlsx or .xls file converts to .csv. There's no separate mode switch to get wrong.
Multiple sheets
CSV is a single-sheet format, so converting to .xlsx always produces a workbook with one sheet. Converting a multi-sheet .xlsx or .xls file only exports one sheet at a time — use the sheet selector that appears for multi-sheet files to choose which one, and download each separately if you need more than one as CSV.
What doesn't carry over
CSV is plain text, so converting an .xlsx to .csv keeps the cell values but drops formulas (only their last calculated result is kept as text), formatting, colors, charts, and multiple sheets. Going the other way, converting .csv to .xlsx, produces a plain workbook with no formatting applied.
Frequently asked questions
Does this work with older .xls files, not just .xlsx?
Yes — both the older binary .xls format and the modern .xlsx format are supported as input. The output when converting to a spreadsheet is always the modern .xlsx format.
What happens to formulas when converting XLSX to CSV?
CSV can only store plain values, not formulas — each formula cell is converted to its last calculated result as plain text, not the formula itself.
Can I convert just one sheet from a multi-sheet workbook?
Yes. If your file has more than one sheet, a sheet selector appears after upload — pick the one you want and the CSV download updates to match. Convert again with a different sheet selected if you need more than one.