Convert CSV to XLSX
To convert CSV to XLSX, drop your CSV file into the converter on this page and press Convert to XLSX. The rows are parsed and written into an Excel workbook inside your browser, so your data never leaves your machine.
Runs in your browser. Your file never leaves your device.Drop your CSV hereChoose a CSV to convert
It becomes a XLSX right in your browser, up to 100 MB
Your file never leaves your device
Works in airplane mode. See the proof
Limits, published exactly
| Where it runs | In your browser. The file never leaves your device. |
|---|---|
| Free conversions | Unlimited. No account, no ads, no queue, no watermark. |
| Max file size, free | 100 MB |
Why convert CSV to XLSX?
CSV is the lowest common denominator for tabular data, but it is awkward to actually work in. Open a CSV directly and you get no column widths, no number formatting, no formulas and no second sheet. Saving it as a proper .xlsx gives you a workbook Excel, Numbers and Google Sheets treat as a first-class document, ready for pivot tables, charts and formatting. It is the natural step when a CSV export from a database or analytics tool has to become something a person edits and shares.
What is CSV?
CSV is the plainest way to store a table: one row per line, fields separated by commas, readable by every spreadsheet and database tool. It carries no formatting, formulas, or multiple sheets, which is exactly why it travels so well between programs. The tradeoff is that anything richer than a flat grid has to be flattened to fit.
What is XLSX?
XLSX is the Excel workbook format introduced with Office 2007: a zip archive of XML sheets, styles and formulas. It is the default container for tabular data in business, but a workbook is a living calculation, not a document, so layouts shift between Excel versions and alternative spreadsheet apps. Exporting to PDF pins the printed view of each sheet so the numbers land in front of the reader exactly once, exactly as formatted.
Quality and what to expect
The conversion fills a single worksheet from the CSV, with the first row read as the header. Values are written as the text and numbers the CSV contained; the workbook adds structure, not new data, so there are no formulas or styling until you add them. Very large files are handled in your device memory like every client conversion here rather than on a server. Long digit strings keep their text form instead of being coerced into scientific notation.
CSV to XLSX FAQ
Does my spreadsheet data get uploaded?
No. The CSV is parsed and the XLSX is built by JavaScript running in your browser tab. Nothing about the contents is sent to a server, which you can confirm in the network tab.
Will it create multiple sheets?
No. A CSV describes one table, so the workbook has one sheet. Combine several sheets afterward in your spreadsheet app if you need them in one file.
Does the header row become column titles?
The first row is written as the top row of the sheet, where headers belong. The conversion does not freeze or style it; do that in your spreadsheet app if you want.