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Runs in your browserConvert Excel to CSV
Excel can already save a single sheet as CSV, but only one at a time, and only the sheet you're looking at. This converts every sheet in one pass and hands them back as a zip. It also means you don't have to open a workbook from a client just to export it.
How to use it
- Choose your .xlsx file.
- Convert every sheet, or just the first.
- Pick a delimiter if you need semicolons or tabs, then click Convert.
Questions
Is my file uploaded anywhere?
No. This page contains the whole tool — the JavaScript that does the work runs inside your browser tab, on your own machine. There is no server to upload to. You can confirm it yourself: open your browser's developer tools, switch to the Network tab, and run the tool. You will not see your file go anywhere. You can also disconnect from the internet after the page loads and it will still work.
What happens to dates?
They're written as YYYY-MM-DD, and dates carrying a time keep it as YYYY-MM-DD HH:MM:SS. That format sorts correctly as text and is unambiguous — unlike 03/04/2026, which is two different days depending on which side of the Atlantic you're on.
Do formulas come out as formulas or as values?
As values — the result Excel last calculated, which is what you want in a CSV. A CSV has no concept of a formula, so exporting the formula text would produce a file full of unusable =SUM() strings.
Will it open an old .xls file?
No. The legacy .xls format is a completely different binary format, not a variant of .xlsx. Open it in Excel or LibreOffice and save as .xlsx first.