Convert CSV to Excel (XLSX) Online Free

Got a CSV export you need as a proper Excel file? AllConvert converts CSV to XLSX instantly, right in your browser. No upload, no account, no Microsoft Office required.

Why convert CSV to XLSX?

CSV is great for moving data between systems, but it is just raw text: no formatting, no multiple sheets, no charts, and Excel sometimes mangles it on open — splitting columns wrong, breaking dates or stripping leading zeros from phone numbers and postal codes. Converting to a real XLSX workbook gives you a file that opens cleanly in Excel, Google Sheets and LibreOffice every time, ready for formatting, formulas and charts.

What happens during the conversion?

AllConvert parses your CSV — handling quoted fields, commas inside values and line breaks correctly — and writes each row into a proper spreadsheet grid in a new XLSX workbook. The result is a standard Excel file with your data in the first sheet, one cell per value.

Round-tripping your data

Need to go the other way later? AllConvert also converts XLSX back to CSV and XLSX to JSON, so you can move freely between spreadsheet and data formats without installing anything.

How to convert

1. Drop your CSV file into the converter box at the top of this page, or click the box to choose it.
2. The XLSX workbook is built straight away, entirely on your device.
3. Click the download button that appears to save the Excel file.

Nothing leaves your device during conversion, so there's no upload wait even for a spreadsheet with tens of thousands of rows. Works in any modern desktop or mobile browser.

What's actually inside an XLSX file

XLSX isn't a single binary blob — it's a zip archive of XML files. The cell grid lives in a part called xl/worksheets/sheet1.xml, the text values it references live in xl/sharedStrings.xml, and a manifest ties the pieces together. Converting CSV to XLSX means building that whole zip structure and writing each value into its own explicit cell. That matters because it sidesteps a classic problem with just renaming a CSV to .xlsx or letting Excel open it directly: Excel's own import applies automatic type-guessing that can turn "1-2" into a date, drop the leading zero from "00501", or flip a long ID number into scientific notation. Writing straight into the worksheet XML keeps each cell exactly as you gave it.

Frequently asked questions

How do I convert a CSV file to Excel without Office?
Drop your CSV into the converter at the top of this page and it converts to XLSX automatically. You get a standard Excel workbook without needing Microsoft Office installed — everything runs in your browser.

Will my data change during the CSV to XLSX conversion?
No. Every row and value from the CSV is written into the spreadsheet as-is, with quoted fields and embedded commas handled correctly.

Is my data uploaded to a server?
No. The conversion runs entirely in your browser using JavaScript — your data never leaves your device, which makes it safe for sensitive spreadsheets.