XLSX to CSV Converter with Sheet Picker and UTF-8 BOM

What this XLSX to CSV converter does

It opens an Excel workbook (.xlsx or .xlsm) directly in your browser, lists every worksheet, and turns the one you pick into CSV text you can copy or download. There is no upload step: the file is unzipped and parsed with JavaScript on your machine, which makes it safe for payroll exports, customer lists and anything else you would rather not hand to a random converter site.

Excel's own "Save As CSV" only exports the active sheet, uses your system's list separator (a semicolon in much of Europe), and on older versions writes the legacy Windows code page instead of UTF-8. This tool always writes UTF-8 and lets you choose the delimiter explicitly, so the output is predictable regardless of locale.

Typical uses are loading a spreadsheet someone emailed you into a database with COPY or LOAD DATA, feeding a sheet to a pandas or R script, preparing an import file for a CRM or e-commerce platform, or diffing two versions of a sheet as plain text in Git.

How values are converted

The converter uses the values Excel saved, not the formulas: a cell containing =SUM(A1:A9) exports as its last calculated result. Numbers are written in full precision without thousands separators or currency symbols, because CSV consumers — databases, pandas, import scripts — expect raw values rather than display formatting. Booleans become TRUE and FALSE, and error cells keep their code, such as #N/A or #DIV/0!.

Dates are stored in Excel as serial numbers (45000 is 15 March 2023), and the only clue that a number is a date is its cell format. The reader inspects the workbook's styles, recognises the built-in date and time formats and custom ones such as dd/mm/yyyy, and writes ISO 8601 values — 2023-03-15, 2023-03-15T09:30:00 or 09:30:00 — which every language parses unambiguously. Excel's historical 1900 leap-year bug and workbooks using the 1904 date system are both accounted for.

Fields that contain the delimiter, a double quote or a line break are quoted and inner quotes are doubled, following RFC 4180, so multi-line cells survive the trip. Empty rows and cells keep their position; trailing empty rows are dropped.

When to add a UTF-8 BOM, and other options

A byte order mark is three invisible bytes at the start of the file that announce "this is UTF-8". Excel on Windows needs it: without the BOM it opens a UTF-8 CSV as the legacy code page and names like Zoë or Müller turn into mojibake. Most programs — Python's csv module, PostgreSQL COPY, command-line tools — do not want it and may read it as part of the first header. Turn the BOM on when a human will reopen the file in Excel; leave it off for code and databases.

Line endings default to CRLF, which RFC 4180 specifies and Excel expects; switch to LF for Unix tooling if you prefer. Legacy binary .xls files (Excel 97–2003) use a completely different format and are not supported — open them in Excel or LibreOffice and save as .xlsx first. Password-protected workbooks are encrypted and cannot be read either.