CSV to Excel Converter

Why not just rename the file?

You’ve got a CSV and someone wants it “in Excel.” Tempting to slap .xlsx on the end and call it done. Don’t. Excel will refuse to open it, or worse, throw a corrupt-file warning, because a real .xlsx is a zipped bundle of XML, not plain text with a different extension.

This converter writes the actual binary. Paste your CSV or load a .csv file, eyeball the preview, then download a workbook Excel opens without a single complaint.

How it works

Three steps, and the middle one is just looking.

1. Drop your data in. Paste into the box, or hit Load .csv file and pick one off your disk. Either way it lands in the same textarea so you can tweak it before converting.
2. Check the table preview. The first row becomes your column headers. To keep big files snappy, the on-screen table shows the first 50 data rows, but every row gets written to the file regardless.
3. Click Download .xlsx. The spreadsheet library loads on demand at that moment (it’s about 900KB, so there’s no point dragging it onto pages that never touch Excel), builds a single sheet named Sheet1, and saves data.xlsx.

The parsing is the part that actually matters. Naive CSV handling splits on every comma and breaks the second a value contains one. This follows RFC 4180 properly:

• A field wrapped in double quotes can hold commas. "New York, NY" stays one cell, not two.
• Escaped quotes work. Inside a quoted field, "" collapses to a single ", so "She said ""hi""" becomes She said "hi".
• Newlines inside quotes survive. A multiline address in one cell stays in one cell instead of spilling into new rows.

A couple of things worth knowing

Every value lands in the sheet as text, exactly as you typed it. That’s deliberate. CSV has no type information, so guessing which strings are “really” numbers or dates is where a lot of converters quietly mangle data, think leading zeros stripped off zip codes or phone numbers, or 03/04 reinterpreted as a date. If you want a column treated as numeric, format it inside Excel after opening, where you can see what you’re doing.

Got a file using semicolons or tabs instead of commas? Swap the delimiter to commas first. This expects standard comma separation.

None of your data leaves the page. The file is read with the browser’s FileReader and the workbook is assembled locally in JavaScript, then handed straight to a download. There’s no server in the loop, which is the whole point when the spreadsheet is a customer list or a payroll export.

Common questions

Is the output a genuine Excel file?

Yes, a real .xlsx (the OpenXML format Excel 2007 and later use). Not a CSV in disguise. It opens in Excel, Google Sheets, LibreOffice Calc, and Numbers.

How many rows can it handle?

Plenty for everyday use. The preview caps at 50 rows so the page stays responsive, but the conversion itself writes all of them. The practical ceiling is your browser’s memory, so tens of thousands of rows are fine, a multi-million-row export less so.

My commas split into extra columns. What happened?

Those values weren’t quoted. In CSV, any field containing a comma has to be wrapped in double quotes, like "Paris, France". If your source skipped the quotes, the structure is genuinely ambiguous and there’s no way to recover the intent. Re-export with proper quoting.

Can I get multiple sheets?

Not from here. Everything goes into one sheet called Sheet1. For a multi-tab workbook you’d build it in Excel directly, or run separate CSVs through and combine them.

Does it work on my phone?

It does. The whole thing runs in the browser, so a CSV pasted on mobile downloads an .xlsx the same as on desktop, assuming your phone has somewhere to save and open it.