CSV to Excel Converter
Note: Excel converts anything that looks like a number or a date as it opens the file, before you can intervene β 007 becomes 7 and 1-2 becomes a date. Only a real spreadsheet file with the column typed as text prevents that; no CSV trick does it reliably.
The first is encoding. Excel on Windows assumes a CSV is in the local ANSI codepage unless the file starts with a UTF-8 byte order mark. Without that mark, every accented character arrives mangled β MΓΌller becomes MΓΒΌller β and no amount of correct data upstream helps. Adding three bytes to the front of the file fixes it entirely, which is why the export here includes them by default.
The second is the delimiter. Excel does not read the commas in a .csv as separators; it reads whatever the machine's regional list separator is. On a German or French system that is a semicolon, so a comma-separated file opens as one column per row. A file can declare its own separator on the first line with a sep= directive, and Excel honours it β that is the reliable way to make one file open correctly on every machine.
The third is type coercion, and it is the destructive one. Excel converts anything resembling a number or a date the moment the file is opened: 007 becomes 7, 1-2 becomes a date in January, and a long identifier becomes scientific notation. The data is changed before you see it, and saving over the file makes that permanent. The only reliable defence is to write a real spreadsheet file that declares those columns as text, which is what the Excel output here does β it produces SpreadsheetML, the XML workbook format Excel opens natively, where a cell can be typed as a string and stays one.
Everything runs in the browser. Spreadsheets are the last thing you should be uploading to someone else's server.
Frequently Asked Questions
Why do accented characters break when Excel opens my CSV?
Because Excel on Windows assumes the local ANSI codepage unless the file begins with a UTF-8 byte order mark. Those three bytes are the entire fix, and the export here includes them by default β the same file then opens correctly in Excel, Numbers and Google Sheets.
Why does my file open as a single column?
Excel splits on the machine's regional list separator, not on commas. On a German or French Windows install that is a semicolon. Putting sep=, on the first line tells Excel which one to use, and it takes precedence over the regional setting.
How do I stop Excel destroying my leading zeros?
Nothing in a CSV can prevent it reliably β Excel converts on open, before you have a chance to intervene. The tricks with a leading apostrophe or an equals sign work only sometimes and pollute the data for every other reader. Use the Excel option here, which writes each affected cell with an explicit string type so the value arrives exactly as you wrote it.
What sort of Excel file does it produce?
SpreadsheetML β the XML workbook format, saved as .xls. Excel opens it natively with the bold header and the text-typed columns intact; it is not a renamed CSV. It is written entirely in the browser, so nothing leaves your machine. If you need the zipped .xlsx specifically, open this and save as that format.
