Convert CSV to Excel
Produces a genuine xlsx file rather than a renamed CSV, so Excel opens it without the “this file is in a different format” warning and without mangling the encoding.
- Runs entirely in your browser
- Works offline
- No upload
- No sign-up
- No watermark
Loading the tool…
How it works
- Drop a .csv, .tsv or .json file.
- Choose Excel as the output.
- Download the .xlsx.
Why nothing is uploaded
Every operation on this page is done by code running inside your browser tab, using the same engine that renders web pages. The file is read from disk into your tab’s memory, transformed there, and written back out as a download. It is never sent anywhere — not to us, not to a third party.
Verify it yourself
- Open your browser’s developer tools (F12) and select the Network tab.
- Load your file and run the tool.
- The only requests you will see are the tool’s own code and, once cached, none at all.
Frequently asked questions
Why not just rename the CSV?
Because Excel then guesses the encoding and the delimiter, which is how Japanese text turns into mojibake and how a leading zero disappears. A real xlsx stores the strings as strings, in UTF-8, with no guessing.
Is the workbook uploaded?
No. SheetJS writes the xlsx inside this tab and hands you the bytes as a download.