CSV to Excel (XLSX)

What it does

Opening a CSV file in Excel is not really opening a file: Excel reads the text and guesses what every cell means. The guesses are often wrong. A product code of 007 becomes 7, a share of 1/2 becomes 2 January, an 18-digit tracking number turns into 1.23E+17 and loses its last digits, a cell that begins with = runs as a formula, and (5) quietly becomes minus five. The file on disk still says 007; the spreadsheet in front of you does not.

This converter writes a real Excel workbook (.xlsx) instead. In that format every cell states its own type, so nothing has to be guessed. Values Excel would change are written as text and appear exactly as you typed them. Ordinary numbers are written as numbers, so SUM, sorting and charts work as usual. Amounts like 12.50, 1,200 and 45% are stored as numbers and shown the way you wrote them, so they both add up and look right.

The first row can be used as a header: it is written in bold and frozen, so it stays visible while you scroll. Cells containing more than one line keep their line breaks, column widths are set from the content, and accents, CJK and other non-Latin text survive because the file is UTF-8 throughout. Everything happens in your browser: choosing a file reads it on your device, and nothing is uploaded, stored or sent anywhere.

How to use it

1. Paste your CSV text into the box, or choose a .csv file from your device.
2. Check the separator if the columns look wrong: comma, semicolon and tab are detected automatically, and you can set it yourself.
3. Turn off First row is the header if your file starts straight into data.
4. Press Download Excel file and open the .xlsx in Excel, Google Sheets, LibreOffice or Numbers. Values shown in colour in the preview are the ones being protected.

Frequently asked questions

Why does Excel change 007 to 7 when I open a CSV?

Because a CSV file contains only text, with no information about what each value is. Excel therefore guesses, and it guesses that a run of digits is a number, which drops leading zeros. The same guessing turns 1/2 into a date and shortens long ID numbers. An .xlsx file records the type of every cell, so this tool can mark those values as text and they stay exactly as written.

Do numbers still work as numbers?

Yes. Only values Excel would visibly change are stored as text. Plain numbers stay numbers, so SUM, averages, sorting and charts work normally. Amounts like 12.50, 1,200 and 45% are stored as numbers with a display format, so they keep their trailing zero, their thousands separator or their percent sign while still adding up.

Is my file uploaded anywhere?

No. Choosing a file reads it inside your browser, and the workbook is built there too. Nothing is sent to a server, nothing is stored, and there is no account. You can disconnect from the internet after the page loads and the tool still works.

Which separators are supported?

Comma, semicolon and tab. The right one is detected by seeing which gives every row the same number of columns, which is why a semicolon file full of comma decimals such as 1,5 is read correctly. You can also choose the separator yourself, including a single-column mode. Quoted fields containing commas, semicolons or line breaks are handled according to the CSV standard.

Can Google Sheets, LibreOffice or Numbers open the file?

Yes. The .xlsx format is the standard spreadsheet format and all of them read it, including the text and number formats that keep your values intact. You can also use Copy for Excel & Sheets to paste the table straight into an open spreadsheet instead of downloading a file.

What about very large files?

The work happens in your browser, so a very large file is limited by your device's memory rather than by a server. Tables of a few tens of thousands of rows convert comfortably. The preview shows the first 30 rows to stay quick, while the downloaded workbook always contains everything.