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Excel to CSV Converter
Pull the first sheet of an Excel workbook out to plain CSV, in your browser — formulas become their values, and nothing is uploaded.
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Quick Answer
Drop an Excel file (.xlsx or .xls) and this extracts its first sheet to plain CSV using the SheetJS library, right in your browser. Formulas are written out as their computed values, and styling, colours and merged cells fall away — CSV holds plain text only. The file is read on your device and never uploaded.
What the Excel to CSV Converter Does
Drag in (or pick) an .xlsx or .xls workbook and the tool converts its first sheet to comma-separated values, ready to copy or download. The conversion is instant and happens on your machine.
CSV is the universal import format — databases, scripts, BI tools and countless apps read it where they may not read a native .xlsx — so this is how you get spreadsheet data into the next system in line.
How It Works
SheetJS reads the workbook (a zipped Office Open XML bundle, or a legacy .xls) in the browser, takes the first sheet, and serialises its cells to comma-separated values, quoting any field that needs it under RFC 4180.
Only the first sheet is converted. Formula cells are emitted as their last-calculated results, and anything visual — fonts, fills, column widths, merged cells — is dropped, because CSV stores values and nothing else.
Data source & conversion logic
No external data. SheetJS parses the Office Open XML (or legacy .xls) workbook in your browser and writes RFC 4180 CSV — nothing is uploaded.
- Step 1. Read the dropped workbook with SheetJS (Office Open XML or .xls).
- Step 2. Select the first sheet.
- Step 3. Convert its cells to CSV, quoting fields that need it per RFC 4180.
- Step 4. Write formula cells as their computed values.
- Step 5. Copy the CSV or download it.
Privacy
The workbook is read in your browser by SheetJS and never uploaded.
Nothing is stored — the data lives only in the open page.
That makes it safe for confidential spreadsheets like budgets or HR data.
Technical Details
| Input | .xlsx or .xls (drag-and-drop) |
|---|---|
| Output | CSV — first sheet only |
| Engine | SheetJS |
| Formulas | Written as their computed values |
| Formatting | Dropped (values only) |
| Encoding | UTF-8 text |
| Where it runs | In your browser — never uploaded |
Standards & references
- Office Open XML / .xls (ECMA-376, ISO/IEC 29500) — the workbook formats SheetJS reads — the modern zipped-XML .xlsx and the legacy binary .xls.
- RFC 4180 — the CSV output rules — comma delimiter with quoting for fields that contain commas, quotes or line breaks.
- SheetJS — the in-browser library that parses the workbook.
Accuracy & Limitations
First sheet only. A multi-tab workbook converts just its first sheet — for the others, use the Excel sheet splitter.
Formulas become values. The CSV captures what each formula evaluated to, not the formula itself.
Formatting is lost by design: colours, fonts, number formats, merged cells and column widths have no equivalent in CSV.
If you reopen the CSV by double-clicking it in Excel, Excel may re-type the values — stripping leading zeros or turning codes into dates. Import via Data → From Text/CSV as Text to avoid that; it's Excel's behaviour, not this tool's.
Real-World Use Cases
Import into a database or script
Get spreadsheet data into a system that reads CSV but not .xlsx.
Feed a data pipeline
Hand a BI or ETL tool the CSV it expects.
Share one sheet lightly
Send a single sheet as a small, universal text file.
Strip down a workbook
Reduce a styled .xlsx to just its values for processing.
When to use it — and when not to
Good for
- Extracting the first sheet to CSV
- Universal import into other systems
- A lightweight text export
- Stripping an .xlsx to plain values
Not the best choice for
- Multi-sheet workbooks
- Keeping formulas, types or formatting
- Very large sheets in a low-memory browser
Need every sheet? Use the Excel sheet splitter. Need to keep formulas, types and formatting? Keep it as .xlsx. Re-importing into Excel? Use Data → From Text/CSV and set the columns to Text.
Frequently Asked Questions
Which sheet gets converted?
The first sheet in the workbook only. The others are ignored in this tool.
How do I convert the other sheets?
Use the Excel sheet splitter, which lists every sheet in the workbook and exports each one to its own CSV.
What happens to formulas?
They're written as their computed values — the number or text the formula produced — because CSV can't hold a live formula.
Is formatting kept?
No. Colours, fonts, number formats, merged cells and column widths are dropped, since CSV is plain text with values only.
Is my file uploaded?
No. SheetJS reads the workbook in your browser, so the file never leaves your device.
Does it read old .xls files too?
Yes — both the modern .xlsx (Office Open XML) and the legacy binary .xls are supported.
Why might Excel mangle the CSV when I reopen it?
Because Excel auto-types columns when it opens a CSV, stripping leading zeros and converting codes to dates. The CSV itself is fine; it's Excel's import behaviour.
How do I keep leading zeros when reopening in Excel?
Don't double-click the file. Use Data → From Text/CSV, then set the affected columns to Text before loading.
Can I copy as well as download?
Yes — copy the CSV from the output box, or download it as a file.
What about very large workbooks?
Everything runs in the browser, so an extremely large sheet is limited by your device's memory. Big files may be slow; very big ones may not fit.
Does it handle commas inside cells?
Yes. Cells containing a comma, quote or line break are quoted in the output per RFC 4180, so the CSV parses correctly.
What encoding is the CSV?
UTF-8 text, so accented characters and non-Latin scripts are preserved.
References
Extracts only the first sheet and writes formula results, not formulas — and the whole conversion happens in your browser, so the workbook is never uploaded.
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