Excel to CSV converter

DataConvert an Excel sheet, or every sheet, to CSV in your browser. Dates, leading zeros and long numbers come out right, and nothing is uploaded.

Your spreadsheet is read on this device and never leaves it. Nothing you open is ever uploaded. There is no server to upload it to.

What this does

It turns a spreadsheet into CSV, the plain-text table format almost every program imports. It reads Excel’s .xlsx, .xlsm and .xlsb, the older .xls, and OpenDocument’s .ods, shows a preview of exactly what will be written, and converts one sheet or all of them.

The file never leaves your browser.

How to use it

  1. Drop a spreadsheet onto the tool, or press “Choose a spreadsheet”.
  2. Pick the sheet, if there are several, and how values should be written: as shown in the spreadsheet, or raw.
  3. Pick a separator, then download the CSV, or every sheet as a zip.

As shown, or raw

Spreadsheets store dates as numbers of days, percentages as fractions, and money as plain numbers, and display them through a format. “As shown” writes what the spreadsheet displays; “raw” writes what it stores, in forms databases and other programs read without guessing. The same cells, both ways:

Cell As shown Raw
A date 09/10/2026 2026-10-09
A time 14:30 14:30:00
Money £1,234.50 1234.5
A percentage 25.6% 0.256
An ID typed as text 00123 00123
A 16-digit number 1234567890123456 1234567890123456
TRUE or FALSE TRUE TRUE

Two things “as shown” does differently from Excel’s own Save as CSV, on purpose. Long numbers in the General format are written in full, where Excel writes 1.23457E+15. And dates in Excel’s built-in short date format, which Excel displays in each viewer’s own order, come out in yours: day first in the UK, month first in the US. What Excel does to a CSV on opening it, zeros, long numbers, dates and accents, and how to stop it, is in Excel and CSV: leading zeros, scientific notation, dates and accents.

Checked against LibreOffice

A converter is only as good as the cases it gets right, so this one is tested against files a real spreadsheet program wrote. LibreOffice built a deliberately awkward workbook: IDs with leading zeros, UK dates and times, pounds and percentages, a comma, quotes, a line break and an emoji inside cells, a 16-digit number, formulas, a division by zero, merged cells and a hidden sheet. It saved it as .xlsx, .xls and .ods, and exported its own CSV of each sheet.

Converted “as shown”, every sheet in all three formats matches LibreOffice’s own CSV byte for byte, apart from two deliberate choices: lines end the way Excel ends them, and a file that starts with the letters “ID” has them quoted, because Excel mistakes such a file for its old SYLK format and refuses to open it. Converted “raw”, every cell matches the value that was put in it. A workbook on the 1904 date system, used by old Mac versions of Excel, converts to the right dates too.

Limitations

Password-protected files cannot be read. Open the file in Excel, remove the password, and convert the saved copy.

Formulas come out as their saved results. A file whose formulas were never calculated, which some programs that generate spreadsheets produce, has no results to write, and those cells come out empty.

Merged cells keep their value in the top-left cell only, with the rest empty, which is how a CSV represents them.

Very large workbooks need memory. The whole file is read in your browser; a workbook of tens of megabytes is fine on a laptop and may be too much for an older phone.

Frequently asked questions

How do I convert an Excel file to CSV?

Drop the .xlsx or .xls file onto the tool. It shows the first rows of the CSV straight away. Pick the sheet if there is more than one, choose how values should be written, and press "Download CSV", or "Download all sheets" for a zip with one CSV per sheet.

Why did my leading zeros or dates change?

Usually because the CSV was opened in Excel afterwards. A CSV holds only text, and Excel reinterprets it on opening: 00123 becomes 123 and anything date-like becomes a date. The file this tool writes keeps 00123 as 00123. To open it in Excel without the reinterpretation, import it with Data, From Text/CSV, and set those columns to Text.

Why does Excel's own CSV show 1.23457E+15 instead of my number?

Excel writes numbers in the General format as it displays them, and it displays long numbers in scientific notation, so its CSV loses the digits of card numbers, IDs and phone numbers stored as numbers. This tool writes them in full.

Comma, semicolon or tab?

Comma is the standard and what most programs expect. Use semicolon for a file that will be opened by Excel in a country that writes decimals with a comma, such as Germany or France, where Excel expects semicolons. Tab gives a .tsv file, useful when the data itself is full of commas.

Can it convert every sheet at once?

Yes. "Download all sheets" gives a zip with one CSV per sheet, named after the sheets. Hidden sheets are included; in Excel files they are marked as hidden in the sheet list.

What happens to formulas?

A CSV holds values, not formulas, so each formula cell is written as its result: the value the spreadsheet last calculated and saved in the file. Formatting, colours, charts and images are not part of a CSV either.

Is my spreadsheet uploaded?

No. The file is read and converted in your browser, which matters for the payroll, customer list or accounts that spreadsheets so often hold. Open your browser's network panel while you use it and you will see nothing carrying your file leave.