Excel to CSV / CSV to Excel Converter — private, in-browser
Convert .xlsx/.xls to CSV or CSV to .xlsx entirely in your browser — pick a sheet, download the result. No upload, files never leave your device.
🔒 Runs entirely in your browser. Your input and output are never sent to a server or stored — fully private.
🔒 Spreadsheets often contain sensitive data — this tool runs 100% in your browser. Your file is never uploaded or sent anywhere.
About this tool
Spreadsheets are among the most confidential files people handle — payroll, customer databases, budgets — which is why this converter never uploads them. Conversion between Excel (.xlsx or .xls) and CSV runs entirely in your browser using the SheetJS library, unlike converter sites that send your workbook to a server first. Drop in an Excel file to download a CSV, or turn a CSV into a proper .xlsx workbook. If a workbook contains several sheets, a picker lets you choose exactly which one to convert. No sign-up, no watermark, no waiting in a queue.
Frequently asked questions
What survives the conversion from Excel to CSV, and what is lost?
The cell values survive — including the last calculated result of every formula — but nothing else does. CSV is plain text holding a single table, so formulas themselves, number formatting, colors, merged cells, charts, images and any additional sheets are all dropped. That is a limitation of the format, not of this converter. Keep the original .xlsx as your source of truth and treat the CSV as a lightweight, data-only export.
Why do some CSVs open with garbled characters in Excel?
Garbled accents or Asian text almost always mean an encoding mismatch: when you double-click a CSV, Excel assumes an old regional code page unless the file says otherwise. CSVs exported by this tool start with a UTF-8 BOM, a tiny marker Excel understands, so they open with every character intact. If a CSV from elsewhere looks scrambled, use Excel's import dialog and select UTF-8 as the file origin instead of double-clicking it.
Do my spreadsheets ever leave my device?
No. The file is parsed in memory by SheetJS, a JavaScript library running inside your browser, and the converted result is generated on the spot — there is no upload, no server-side queue and no stored copy. That makes it safe for exactly the files people hesitate to put into online converters: salary sheets, client lists, accounting exports. It even works offline once the page has loaded.