Turn an .xlsx worksheet into CSV free, with a choice of separator. No Excel licence, no signup, and the formulas become their results.

How it works

The archive's central directory is read to find two members, and only those two are inflated: xl/sharedStrings.xml and the first worksheet. Cells marked with type "s" hold an index into that shared table rather than their own text, so the two have to be read together. Column positions come from each cell's reference — A1, BC7 — decoded as base twenty-six, because a cell that is empty is simply absent from the XML rather than present and blank.

What to watch out for

Formulas arrive as their last calculated result

A workbook stores both the formula and the value Excel computed the last time it opened the file. CSV has no concept of a formula, so the value is what you get. If the file was never opened after its formulas were written, some cells may be empty for that reason alone.

Only the first worksheet is converted

CSV is a single table by definition, so a workbook with several tabs has to lose all but one. The first sheet in the file is used. Splitting a multi-sheet workbook means saving each tab separately from Excel first, which is a limitation of the destination format rather than of this tool.

Formatting is not data, and does not survive

A date displayed as 31/12/2026 is stored as the number 46387 with a display format attached, and a currency column is a plain number that Excel decorates. CSV carries values, so those cells come out as the numbers underneath. Widths, colours, merged cells and frozen panes all vanish too.

Limits

Files up to about 50 MB work reliably. Beyond that, the ceiling is your device's memory rather than any rule we impose — the work happens on your own machine. Tested in Chrome 140, Firefox 143, Safari 18.

Why the separator matters more than it should

CSV stands for comma-separated values, and in much of the world Excel does not use commas.

In locales where the decimal point is a comma — most of continental Europe, and a good deal of South America — Excel writes and expects semicolons instead, because a comma is already busy separating the whole part of a number from its fraction. Hand such an installation a comma-separated file and it will place every row into a single cell, which looks like a broken export and is really a locale mismatch.

If your CSV opens as one long column, come back and pick the semicolon. It is the single most common thing that goes wrong with this conversion, and it has nothing to do with the file being correct.

Tab-separated is the safe third option: no locale uses a tab as a decimal mark, so a tabbed file opens correctly almost everywhere, and most tools that accept CSV accept it too.

Where the words actually live in a spreadsheet

This is the part that surprises people who open an .xlsx expecting to find their data.

Excel stores text once, in a shared string table, and every cell that shows that text holds a number pointing into the table. A sheet of ten thousand rows where the same twelve category names repeat stores twelve strings and ten thousand small integers.

That is excellent for file size and it means the worksheet XML on its own is close to meaningless — a page of indices. Both parts have to be read and joined, which is what this tool does and what a naive extractor gets wrong.

What CSV cannot carry

Worth knowing before you convert, because none of it is recoverable afterwards.

Formulas become their results. The workbook holds both, but a CSV file has no way to express a calculation, so the value wins.

Formatting is not data. A date is stored as a count of days and displayed through a format; a currency is a plain number with a decoration attached. Both arrive as the underlying numbers, which is technically the truth and often not what you were looking at.

Everything else — column widths, colours, merged cells, filters, charts, comments, additional sheets — has nowhere to go in a plain text table.

That is the honest trade. CSV is the format that every tool on earth can read precisely because it carries almost nothing beyond the values themselves.

Nothing is uploaded

The archive is opened and the XML parsed inside a Web Worker in your browser. Spreadsheets are where salaries, customer lists, patient records and financial models live — the category of file where “we process it on our servers” should give anyone pause. Nothing here is transmitted, and the workbook on your disk is never modified.

Your files never leave your browser. Last updated 2026-08-02.

Convert an Excel sheet to CSV