Tablizer

Convert XLSX to CSV Online

Convert an .xlsx workbook to CSV without uploading it. The file is opened by JavaScript on this page, converted, and never sent anywhere.

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The output will appear here once there is a table to convert.

What XLSX is

An Excel workbook is a zip archive of XML parts describing sheets, cells, formulas, styles and charts. The .xlsx extension is that format; .xls is the older binary one from before 2007.

Finance, operations and anyone who received a file from finance or operations.

What CSV is

CSV is a text file where each line is a row and commas separate the fields. There is no type system, no formatting and no second sheet. Every value is text until something downstream decides otherwise.

Almost every database, analytics tool and spreadsheet can read and write it, which is why exports default to it.

What changes when you convert XLSX to CSV

Only the first sheet is read, and cells are read as the text Excel displays rather than the number underneath. That matters for dates: a cell showing 15/03/2026 arrives as that string, not as a serial number you would then have to decode.

Any value containing the delimiter, a quote or a line break gets wrapped in quotes, and embedded quotes are doubled. That is the rule in RFC 4180 and it is what spreadsheet software expects.

.xlsx is a zip archive of XML parts, which is why the file is larger than the data in it and why unzipping one shows you a folder of sheets, styles and shared strings. Reading it means unpacking that archive and walking the sheet XML, which is what happens here.

The conversion keeps values and drops everything that describes how they look. Styles live in a separate part of the archive from the cell data, so leaving them behind is not a compromise, it is the natural result of reading only the sheet.

A workbook can hold many sheets and a CSV cannot. The first sheet is used.

What carries over from XLSX to CSV

Excel records 3 things about a table that CSV has no way to hold.

Excel distinguishes a number from the text of a number; CSV does not, so every value arrives as text and has to be re-parsed by whatever reads it next.

An empty cell and a missing one are the same thing in CSV, so a null and an empty string in the Excel both come out blank and can no longer be told apart.

Anything visual in the Excel - weight, alignment, colour, column widths - has no counterpart in CSV and is dropped. The values are what survives.

The result can be read a record at a time, and appended to by adding to the end of it. That is worth having for a table too large to hold in memory, and it means a CSV file that is cut off part way through still gives you every record before the cut.

A worked example

Three rows of staff data, with an identifier that has a leading zero, a value containing a comma, a value containing quotes and one blank cell. Those are the four places formats disagree, so they are the four places to look.

XLSX in
id,name,role,started,hours
007,Halima Yusuf,"Analyst, data",2024-03-15,38.5
012,"Jonah ""Jo"" Pryce",Engineer,2025-11-02,
104,Wei Chen,Manager,2023-06-30,40
CSV out
id,name,role,started,hours
007,Halima Yusuf,"Analyst, data",2024-03-15,38.5
012,"Jonah ""Jo"" Pryce",Engineer,2025-11-02,
104,Wei Chen,Manager,2023-06-30,40

Questions

How do I convert XLSX to CSV?

Paste your XLSX into the box above or drop the file onto it. Check the table in the grid, then copy or download the CSV from the output panel. It takes one step and the data never leaves your browser.

Does converting to Excel keep my formulas?

No. A table has values, not formulas. If your source came from Excel in the first place, the formulas were already resolved to their results before they reached this page. Anything that was =SUM(A1:A10) arrives as the number it produced.

Why does my CSV open with all the data in one column?

The file uses a delimiter your spreadsheet did not expect. Exports from European locales often use semicolons because the comma is the decimal separator there. Change the delimiter in the export options and the columns split correctly.

What is the difference between .xlsx and .xls?

Excel 2007 replaced the old binary .xls with .xlsx, a zip of XML files. The new format handles more than 65,536 rows, compresses better and can be read by tools that do not know anything about Excel internals. Both are read here.

Will my numbers still be numbers?

They will read the same, but CSV stores them as text. Anything that sorts or sums the result will need to parse them first, and a leading zero or a currency symbol is the usual place that goes wrong.

Is there a limit on file size?

No. The work happens on your own machine, so the limit is your machine's memory rather than an upload cap. A file with tens of thousands of rows converts in a second or two.

Is my data uploaded anywhere?

No. The parsing and generating are done by JavaScript running on this page. You can watch the network tab while you convert and see that nothing is sent.

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