Drop an Excel file, pick a sheet (or convert every sheet at once), and download CSV that opens cleanly anywhere. Everything runs locally — nothing is ever uploaded.
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XLSX
What This Tool Does
This tool converts an Excel XLSX workbook into CSV without leaving your browser. Drop your file, and the tool reads its sheet names so you can pick exactly which one to convert — or use convert-all-sheets to turn every sheet in the workbook into its own CSV file in one pass.
Nothing is uploaded to make this happen. A WebAssembly module loaded into your browser tab reads the workbook, walks the sheet you selected, and writes CSV bytes entirely on your own device.
Tip:Working with a multi-sheet report? Use convert-all-sheets to get one CSV file per sheet in a single pass, each named after its sheet, rather than repeating the drop-and-convert steps once for every tab in the workbook.
Picking a Sheet, or Converting Them All
Real workbooks often carry several sheets — a summary tab, a few months of raw data, maybe a lookup table tucked in the back. Once you drop your file, this tool reads the sheet names straight out of the workbook and shows them in a picker, so you can convert exactly the one you need without guessing which tab is which. If you'd rather have everything at once, convert-all-sheets loops through the whole workbook and hands you back one CSV per sheet, each file named to match.
Reading XLSX, and What's Not Supported Yet
This version reads modern XLSX workbooks — the format Excel, Google Sheets, and LibreOffice all save by default today. It doesn't yet open the older binary XLS format or OpenDocument's ODS format; if you're starting from one of those, saving or exporting a copy as XLSX first in whichever program you have open will get you a file this tool can read. This is a scoped limitation of the current version, not a silent failure — an unsupported or corrupted file produces a clear error rather than a broken CSV.
Dates, Encoding, and What Lands in Your CSV
Two details worth knowing before you convert a real-world sheet. First, the CSV output carries a UTF-8 byte-order mark at the start of the file specifically so Excel opens Vietnamese and other accented text correctly rather than mangling it — a classic gap in plainer CSV exports. Second, date and time cells currently convert to their raw underlying serial number rather than a formatted date, since that's the value Excel stores internally; this is a known limitation of the current version rather than a formatting bug, and a fix for readable dates is on the roadmap. Numbers, text, and boolean cells all convert as you'd expect, and an empty or error-displaying cell simply becomes a blank value rather than breaking the conversion.
Where to Go Next
Need to go back the other way? CSV to Excel turns a CSV or TSV file into a real XLSX workbook, with numeric columns written as actual numbers. If your workflow runs through JSON instead of spreadsheets, CSV to JSON and JSON to CSV cover conversions on that side.
Frequently asked questions
What Excel file formats can I convert?
This version reads XLSX workbooks — the format modern Excel saves by default. The older binary XLS format and OpenDocument's ODS format aren't supported yet; if your file is in one of those, open it in Excel, LibreOffice, or Google Sheets and save or export a copy as XLSX first, then drop that file in here.
My workbook has several sheets — which one gets converted?
After you drop your file, the tool reads its sheet names and shows them in a picker, so you choose exactly which one to convert. If you need all of them, use the convert-all-sheets option instead, which runs through every sheet in one pass and gives you back one CSV file per sheet, matching the sheet's name.
Why does the CSV open correctly with Vietnamese or other accented text, instead of showing broken characters?
Every CSV this tool produces starts with a UTF-8 byte-order mark, a few invisible bytes at the very beginning of the file. Excel checks for that marker to know the rest of the file is UTF-8 text; without it, Excel often guesses a different encoding and diacritics come out as garbled symbols. Other text tools simply ignore the marker, so it doesn't cause problems anywhere else.
How do dates come through in the converted CSV?
As Excel's underlying serial number rather than a formatted date string — this is a known limitation of the current version. Excel stores dates internally as a count of days (plus a fractional part for time) from a fixed starting point, and that's the raw value you'll currently see in the CSV rather than something like 15/07/2026. If you need readable dates today, you can reformat that column after conversion; proper date formatting is on the roadmap.
What happens to empty cells or cells showing a formula error in the original workbook?
Both come through as an empty value in the CSV rather than causing the conversion to fail. An empty cell stays empty, and a cell displaying an error like a broken reference converts to a blank cell too, so one problem cell won't stop the rest of your sheet from converting.
Is my workbook uploaded anywhere to be converted?
No. The whole conversion — reading the workbook, listing its sheets, and writing the CSV — runs through a WebAssembly module loaded into your browser tab, entirely on your own device. Nothing about your file is sent over the network.