Convert a CSV file to an Excel workbook (.xlsx) locally - no upload, right in your browser. Your data stays on your device.
Running locally on your device ...
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Your files never left your device
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
An .xlsx file is the native format of Microsoft Excel and also opens in LibreOffice, Numbers and Google Sheets with proper columns and cells. Turning a CSV into a real Excel workbook saves the error-prone manual import - numbers, text and columns land cleanly in a worksheet.
This tool parses the CSV entirely locally in your browser (papaparse) and writes a real .xlsx workbook (SheetJS, pure JavaScript). The first row is taken like any other row - you keep your header. Nothing is uploaded, it even works offline.
An important caveat: a plain CSV carries no font sizes, colours, charts or calculation formulas, so what arises here is a simple value table - not a finished, styled report sheet. What you gain is the clean recognition of numbers as real numbers, which Excel can then immediately sort, filter or sum. You add styling and formulas afterwards conveniently in the spreadsheet program itself.
| Input formats | CSV |
|---|---|
| Output format | XLSX |
| Batch processing | No |
| Processing | Locally in your browser (JavaScript) |
| File upload | None |
Limitations: Creates a workbook with one worksheet. Numbers are detected as numbers, everything else as text - without cell formatting, formulas or charts. Very large CSVs need memory. The delimiter is auto-detected (comma/semicolon/tab).
No. The Excel workbook is built entirely locally in the browser.
The first row is taken as a normal data row - your header stays intact.
Comma, semicolon and tab are auto-detected.
Yes, it is a standards-compliant .xlsx and opens in Excel, LibreOffice and Google Sheets. Mind the format limit: one worksheet holds at most 1,048,576 rows and 16,384 columns - anything beyond that Excel will not display. For data of that size, CSV stays the more practical format.