Can it open the old .xls format?

No. .xls is the Excel 97-2003 binary format, which has nothing in common with .xlsx. Open it in Excel, WPS or LibreOffice, save as .xlsx and come back.

What happens to formulas?

You get the value the formula produced. Excel stores the computed result alongside the formula, so =SUM(A1:A9) exports as the number. Files written by scripts sometimes carry no cached result; those cells fall back to the formula text rather than exporting a blank.

Why did a percentage become 0.123?

The cell really holds 0.123 and 12.3% is only a display format. Exporting the stored value keeps the numbers usable in code; add percent signs afterwards if you need them.

How are merged cells handled?

They are flattened using the top-left value: the first cell keeps the content and the rest are empty, so the grid still matches CSV rows and columns. The preview tells you how many merged ranges there were.

Is there a row limit?

No. Parsing walks the XML in order, so sheets with tens of thousands of rows work; only the preview is capped at the first 30 rows and 12 columns to keep the page responsive.

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When a spreadsheet has to feed a script, go into a document or land in a Git repository, what you actually need is the plain data. This tool parses xlsx right in the browser: pick a file, look through each worksheet, then choose an output format. The spreadsheet never leaves your machine, so company data is safe here.

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How to use Excel Converter

1Choose an .xlsx / .xlsm file
2Switch worksheets with the tabs above the preview
3Pick CSV / TSV / JSON / Markdown / HTML, then copy or download

FAQ

Can it open the old .xls format?: No. .xls is the Excel 97-2003 binary format, which has nothing in common with .xlsx. Open it in Excel, WPS or LibreOffice, save as .xlsx and come back.
What happens to formulas?: You get the value the formula produced. Excel stores the computed result alongside the formula, so =SUM(A1:A9) exports as the number. Files written by scripts sometimes carry no cached result; those cells fall back to the formula text rather than exporting a blank.
Why did a percentage become 0.123?: The cell really holds 0.123 and 12.3% is only a display format. Exporting the stored value keeps the numbers usable in code; add percent signs afterwards if you need them.
How are merged cells handled?: They are flattened using the top-left value: the first cell keeps the content and the rest are empty, so the grid still matches CSV rows and columns. The preview tells you how many merged ranges there were.
Is there a row limit?: No. Parsing walks the XML in order, so sheets with tens of thousands of rows work; only the preview is capped at the first 30 rows and 12 columns to keep the page responsive.