Turn a plain CSV file into a proper .xlsx workbook you can open and format in Excel. Converts in your browser — nothing uploaded. Free.
🔒 Runs entirely in your browser — your data never leaves your device.
CSV is universal but bare — no formatting, no formulas, and awkward quirks when you double-click it (leading zeros vanish, long numbers become scientific notation, dates reinterpret themselves). Converting to a real .xlsx gives you a proper spreadsheet to format, chart and calculate in, and this conversion is perfect-fidelity because both formats simply hold rows and columns of data. Exports from your bank, POS, or analytics that arrive as CSV become workbooks in one click.
Need to go the other way? Excel to CSV. Want a PDF of the data instead? Excel to PDF. For quick data reshaping, the CSV to JSON tool helps developers.
Is my data uploaded?
No — the CSV is read and rewritten as .xlsx inside your browser. Nothing is sent to a server, so it's safe for financial and personal data.
Does it fix the "leading zeros disappearing" problem?
Converting to .xlsx preserves your cell values as written far better than double-clicking a CSV. For fields like postcodes or IDs, format the column as Text in Excel afterwards to lock them.
Will it handle commas inside fields?
Yes — properly quoted CSV fields containing commas are parsed correctly and land in a single cell.
What about semicolon-separated files?
Standard comma CSVs work best. If your file uses semicolons (common in some regions), the parser handles common delimiters, but comma-separated is the most reliable input.
Can I open the result in Google Sheets?
Yes — the .xlsx opens in Excel, Google Sheets, LibreOffice, and Numbers.