Drop in an Excel file, preview the sheet in your browser, and download it as CSV, JSON, or TSV. The whole thing runs locally with the open-source SheetJS library, so your spreadsheet never leaves your device — which matters when the data is payroll, customers, or anything you can't email around.
What goes in, what comes out
Accepts: .xlsx (Excel 2007+), .xls (Excel 97–2003), and .csv. Multi-sheet workbooks are supported — pick the sheet to export from the tabs.
Outputs:
- CSV — Universal plain text. Opens in Excel, Google Sheets, and virtually every database or data tool. The safe default.
- JSON — An array of objects keyed by the first row's column headers. Feed it straight into a script, an API, or a database import.
- TSV — Tab-separated. Better than CSV when your cells contain commas, like addresses or free-text descriptions.
XLSX vs CSV: what you keep and what you lose
This trips people up, so it's worth being blunt. XLSX is Excel's full format — it stores multiple sheets, live formulas, cell colors and fonts, number formats, merged cells, and charts. CSV is just text: rows of values separated by commas, one table, nothing else.
Converting to CSV or JSON therefore drops:
- Formulas — a cell of
=SUM(A1:A10)becomes its current result, e.g.420. The formula itself is gone. - Formatting — colors, bold, borders, and merged cells vanish.
$1,200.00may export as1200. - Extra sheets — CSV holds one table, so you export each sheet separately.
Keep the original XLSX
CSV is a one-way trip for anything but raw values. If you might need those formulas, pivot tables, or formatted reports again, don't treat the CSV as your master copy — save the .xlsx alongside it. Re-deriving lost formulas from values is painful.
When to pick which format
- CSV — a human will open it in a spreadsheet, or you're importing into a tool that expects tabular text. When in doubt, this.
- JSON — the data is headed into code: a JavaScript app, an API payload, a NoSQL import.
- TSV — your values are full of commas and CSV keeps misaligning the columns.
Watch for commas and leading zeros
Two classic CSV gotchas: a value containing a comma (like "Amsterdam, NL") must be quoted or it splits into two columns — a good reason to use TSV. And ZIP codes or IDs with leading zeros (02139) can be read back as numbers (2139) by whatever opens the file. If that bites you, import as text rather than letting the app auto-detect types.
FAQ
What's the difference between XLSX and CSV?
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XLSX is Excel's native format and stores everything — multiple sheets, formulas, formatting, and charts. CSV is plain text holding only raw values in one table, with no formulas or styling. CSV is universal and tiny; XLSX is rich but proprietary.
Does converting to CSV lose formulas and formatting?
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Yes. Formulas become their current calculated values, and all formatting is dropped. CSV and JSON store data only. Keep the original XLSX if you'll need the formulas later.
When should I export JSON instead of CSV?
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Pick JSON when the data feeds code — a script, an API, or a JSON database import. Each row becomes an object keyed by your header names. Pick CSV when a person will open it in a spreadsheet.
Is my file uploaded to a server?
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No. Parsing happens entirely in your browser with the open-source SheetJS library. Nothing is uploaded, so it's safe for confidential financial, HR, and customer data.
Can it handle multi-sheet workbooks?
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Yes. Choose the sheet to export from the tabs. Because CSV and JSON each hold a single table, you convert one sheet at a time.