Are my XLSX files uploaded anywhere?

No. This conversion runs entirely inside your browser, so the file never leaves your device. You can confirm it yourself: open the network tab of your browser's developer tools and watch that nothing is sent while the file converts.

What happens to a workbook with several sheets?

Only the first is converted. A CSV holds one table, so there is no honest way to represent three sheets in one file — and silently concatenating them would corrupt the data rather than lose it. If you need several, save them as separate files in the spreadsheet first.

Are formulas included?

You get the calculated values, not the formulas. That is almost always what an import wants.

What about formatting, colours and merged cells?

All gone. CSV holds values and nothing else — no fonts, no colours, no column widths. A merged cell contributes its value once and leaves the other positions empty, which is worth checking if your sheet uses merges for layout.

What encoding is the CSV written in?

UTF-8, without a byte-order mark. Every modern import expects that. Excel on Windows is the exception: double-clicking a UTF-8 CSV can garble accented characters, so use Data → From Text/CSV and choose UTF-8 rather than opening the file directly.

Do I need Excel installed?

No. The workbook is read by a JavaScript library running in your browser, so this works on a machine that has never had Office on it — which is frequently the reason people are looking for a converter in the first place.

Is the workbook uploaded?

No, it is read entirely in your browser. That matters here more than almost anywhere else: spreadsheets are usually the most sensitive files an organisation has.

XLSXtoCSV

Convert XLSX to CSV

Up to 3 files at once, 100 with Pro. Mixed formats are fine.

Converting XLSX to CSV pulls the values out of the first sheet and writes them as a UTF-8 file: calculated results rather than formulas, and no formatting, colours or column widths. It runs entirely in your browser, so you need neither Excel installed nor the nerve to upload a customer list.

Why an import wants CSV rather than XLSX

The reason for doing this is nearly always a system on the other end: a database import, a script, an upload form, a tool that predates Excel formats. CSV is the plainest possible table — values, commas, line breaks — and its plainness is exactly why everything accepts it.

What a spreadsheet loses on the way to CSV

Everything a spreadsheet does beyond holding values. Formatting, colours, column widths, frozen panes and cell comments have nowhere to go. Formulas are resolved to their calculated results, which is what an import wants. Merged cells contribute their value once and leave the remaining positions empty, which is worth checking if your sheet uses them for layout.

Multiple sheets: only the first one converts

This is the limit to know before you start. A CSV holds one table and a workbook can hold twenty, so only the first sheet is converted. There is no honest alternative — concatenating several sheets into one file would produce something that looks like data and is not.

If you need several, save them separately in the spreadsheet first and convert each one. It is two extra minutes and it is the difference between an import that works and one that fails halfway through with a column count error.

Encoding, and the Excel double-click trap

The CSV is written as UTF-8 without a byte-order mark, which is what every modern importer expects. Excel on Windows is the awkward exception: double-clicking a UTF-8 CSV can turn accented characters into mojibake, because Excel guesses the encoding from the system locale rather than reading it.

The fix is to import rather than open — Data → From Text/CSV, then pick UTF-8. Nothing is wrong with the file; Excel is simply reading it with the wrong assumption.

Converting a workbook without uploading it

This runs entirely in your browser. Spreadsheets are frequently the most sensitive files an organisation has — payroll, customer lists, pricing — and there is no reason for one to travel anywhere to have its commas rearranged. It also means no Office installation is required, which is often why the search happened at all.

How to convert an Excel file to CSV without Excel

Drop your XLSX onto this page, or click to choose it.
The first sheet is read and converted in your browser.
Download the CSV.

XLSX vs CSV: a workbook against one plain table

XLSX compared with CSV
	XLSX	CSV
Full name	Excel Workbook	Comma-Separated Values
File extension	.xlsx	.csv
Media type	application/vnd.openxmlformats-officedocument.spreadsheetml.sheet	text/csv

Quality: Nothing is lost. The result holds exactly the same picture, text or data as the original.
Where it runs: This conversion runs inside your browser. Your file is never uploaded, and it works with the network disconnected.

XLSX to CSV: sheets, formulas and encoding

Are my XLSX files uploaded anywhere?: No. This conversion runs entirely inside your browser, so the file never leaves your device. You can confirm it yourself: open the network tab of your browser's developer tools and watch that nothing is sent while the file converts.
What happens to a workbook with several sheets?: Only the first is converted. A CSV holds one table, so there is no honest way to represent three sheets in one file — and silently concatenating them would corrupt the data rather than lose it. If you need several, save them as separate files in the spreadsheet first.
Are formulas included?: You get the calculated values, not the formulas. That is almost always what an import wants.
What about formatting, colours and merged cells?: All gone. CSV holds values and nothing else — no fonts, no colours, no column widths. A merged cell contributes its value once and leaves the other positions empty, which is worth checking if your sheet uses merges for layout.
What encoding is the CSV written in?: UTF-8, without a byte-order mark. Every modern import expects that. Excel on Windows is the exception: double-clicking a UTF-8 CSV can garble accented characters, so use Data → From Text/CSV and choose UTF-8 rather than opening the file directly.
Do I need Excel installed?: No. The workbook is read by a JavaScript library running in your browser, so this works on a machine that has never had Office on it — which is frequently the reason people are looking for a converter in the first place.
Is the workbook uploaded?: No, it is read entirely in your browser. That matters here more than almost anywhere else: spreadsheets are usually the most sensitive files an organisation has.