Convert CSV files to XLSX free in your browser — no signup, no install, and the file is never uploaded to a server. XLSX keeps full quality with no further loss.
Add your CSV file
Drag the CSV file onto the drop area above, or click it to pick a file from your device. You can add several files at once.
Confirm XLSX as the output
XLSX is already selected as the output format on this page. Only the options this format actually supports show up, such as a page range or sheet selection.
Run the conversion
Press the convert button. Processing happens on your own device, so the time depends on your computer rather than a server queue.
Download the XLSX file
When it finishes, download the XLSX file. Converting multiple files gives you the option to download them together as a ZIP.
The simplest tabular format: one row per line, columns separated by commas. Every program and language can read it, making it the lingua franca of data exchange.
Microsoft Excel's standard format, preserving formulas, charts, multiple sheets, and formatting. Internally it is a zip archive of XML.
Yes. CSV to XLSX conversion is completely free with no signup, no watermark, and no daily limit on the free plan for ordinary use.
No. The conversion runs entirely inside your browser using WebAssembly, so the CSV file never leaves your device. That is also why it works without an internet connection once the page has loaded.
It can go either way. Both formats are lossless, so nothing is thrown away — the size difference comes from how each one packs the same data.
The free plan handles files up to 200MB. Because processing happens on your own device, very large files depend on your computer's memory rather than a server quota.
Spreadsheet converter
What each file format is, what it is used for, and which formats it can be converted to.
Open converter Browse the full format reference