CSV to Excel (XLSX) Converter
Turn CSV data into a proper Excel workbook
To convert CSV to XLSX, drop your CSV files above and click Convert to XLSX. Fylo reads the data with SheetJS in your browser, recognises numbers and dates, and saves a real Excel workbook that opens in Excel, Google Sheets, Numbers and LibreOffice. Your data never leaves your device.
Drop documents here
or tap to browse · paste with Ctrl+V · add many at once
Your files never leave your device
How to convert CSV to XLSX
Add CSV files
Drop one or more .csv files.
Convert
Click Convert to XLSX.
Open in Excel
Download the workbook and open it in any spreadsheet app.
Why convert CSV to Excel?
Opening a CSV directly in Excel can mangle data: long numbers turn into scientific notation, leading zeros disappear and some regional settings split columns incorrectly. Converting to XLSX first gives you a workbook where each value has a proper type, ready to format, filter, chart and share.
How values are handled
SheetJS parses the CSV according to RFC 4180 (quoted fields, embedded commas and line breaks) and stores numbers as numbers and recognisable dates as dates. Everything lands on one sheet, named after the file's first sheet. Text that looks like a number but should stay text — such as phone numbers with a leading +— may need formatting as text afterwards.
Learn more: CSV format guide · XLSX format guide
| Property | CSV | XLSX |
|---|---|---|
| Type | Plain-text table | Spreadsheet workbook |
| How it's stored | None (plain text) | ZIP of XML files |
| Keeps formatting | No — values only | Yes — formulas, formats, multiple sheets |
| Compatibility | Universal: spreadsheets, databases, code | Excel, Google Sheets, LibreOffice, Numbers |
| Best for | Importing and exporting data | Calculations, data with formatting, multiple sheets |
| Introduced | 1972 (RFC 4180 in 2005) | 2007 |
Frequently asked questions
Will Excel open the file without warnings?
Yes — it's a standard .xlsx workbook.
Does it support semicolon-separated files?
Comma-separated works best; semicolon files may need a quick find-and-replace first.
Is there a row limit?
Excel's own limit is 1,048,576 rows; very large files depend on your browser's memory.
Is my data uploaded?
No, conversion happens on your device.
Will my leading zeros be kept?
Values with leading zeros that look like numbers, such as 00123, may be turned into numbers. Format the column as text in Excel if you need them.
Can I convert several CSVs into one workbook?
Not yet — each CSV becomes its own XLSX file. You can copy sheets between workbooks in Excel.
Are my files uploaded to a server?
No. CSV to XLSX runs entirely in your browser — your files are processed on your own device and never sent anywhere. Once the page has loaded, it even keeps working if your connection drops.
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