Convert without uploading
CSV is the universal language of data: nearly everything can read it, from databases and accounting packages to Python scripts and ancient in-house systems. Excel files are the opposite, rich but proprietary. Converting between the two is one of the most common data chores there is, and most online converters do it by uploading your spreadsheet to their server first. This tool does not. The file is opened and converted by JavaScript running in your browser, so your spreadsheet never leaves your device, and once the page has loaded the converter works entirely offline.
Drop a .xlsx or .xls file above. The first sheet is converted straight away, with a preview, a copy button and a .csv download. If the workbook has more than one sheet, buttons appear so you can convert each sheet in turn.
What CSV keeps and what it loses
A CSV file is nothing but the values, one row per line, separated by commas. That simplicity is exactly why everything can read it, and it also means the conversion is one-way for everything else in your workbook. Formulas are exported as their last calculated result, so a cell containing a formula gives you the number it displayed, not the recipe that produced it. Formatting goes too: colours, bold headers, column widths, merged cells, conditional formatting, charts and comments all vanish. And because a CSV holds exactly one table, the other sheets in the workbook are not included; convert and download each one separately using the sheet buttons.
None of this harms the data itself, but keep the original workbook if you ever need the formulas or formatting back. The CSV is a snapshot of what the sheet showed, nothing more.
Worked examples
The Excel date gotcha
Excel stores every date as a serial number counting days, and only the cell's display format makes it look like a date. Naive converters export the raw serial, which is how people end up with a column of numbers like 45658 where 1 January 2025 used to be.
This tool reads date cells properly and writes them out using the display format saved in your file, so dates arrive readable. The format follows whatever the spreadsheet specified, so a sheet saved with American settings exports American-style dates; check a couple of rows before feeding the file into anything fussy.
One final trap worth knowing: the danger runs the other way too. If you double-click a CSV and let Excel open it, Excel guesses types on the way in, stripping leading zeros from phone numbers and quietly reformatting anything that looks vaguely like a date. The file this tool produces is fine; it is Excel's import that mangles things. If you need to go back the other way safely, the CSV to Excel converter linked below builds a proper .xlsx without the guesswork.
Frequently asked questions
Is my spreadsheet uploaded anywhere?
No. The file is opened and converted entirely in your browser with JavaScript. It never leaves your device, nothing is stored, and once the page has loaded the converter works without an internet connection.
What happens to my formulas?
CSV is plain text, so formulas cannot survive. Each formula cell is exported as its last calculated value, the same number you saw in Excel. The formula itself, along with all formatting, colours and column widths, is lost. Keep the original workbook if you need them back.
My workbook has several sheets. What do I get?
A CSV file holds exactly one sheet, so the tool converts one sheet at a time. If the workbook has more than one sheet, buttons appear so you can switch between them, up to 8 sheets. Download each sheet you need as its own file.
Why do my dates look different in the CSV?
Excel stores dates as serial numbers, such as 45658 for 1 January 2025, and only the display format makes them readable. This tool exports dates using the format saved in your file, so you get readable dates rather than serials, but the style follows whatever the spreadsheet specified.
Will commas inside my data break the file?
No. Any value containing a comma, a quote or a line break is wrapped in double quotes, with inner quotes doubled, following the standard CSV rules. Software that parses CSV properly will read it back as one field.