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CSV to Excel
Convert CSV to XLSX format
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CSV to Excel converts a .csv file into a proper .xlsx workbook — the format Excel, Google Sheets and every spreadsheet app opens natively with typed cells. It runs on your device using the bundled xlsx engine; the data never leaves your computer.
Use it to hand data to someone in a friendlier format, to open CSVs in tools that only accept .xlsx, or as the first step before sorting and charting in Excel.
How To Use CSV to Excel Offline
- Open CSV to Excel — Under File Tools, or search "csv" with ⌘/Ctrl+K.
- Drop your CSV — Drag the file in. The delimiter-separated rows become a worksheet.
- Process — The .xlsx lands in your output folder — ~/Documents/1FileTool by default.
- Open it — Open the workbook in Excel, Numbers or LibreOffice — rows and columns parse cleanly.
Why Use 1FileTool Over Online Tools?
- 100% offline — Files never leave your computer. No uploads, ever.
- Pay once — One-time payment from $29. No monthly subscriptions.
- Instant results — Local processing is faster than uploading + server processing + downloading.
- No file size limits — Process files of any size, limited only by your disk space.
- GDPR compliant — No data collection means complete privacy compliance by design.
Formats
| Input | Output | Notes |
|---|---|---|
| .csv | .xlsx | Also available in reverse: Excel to CSV, plus CSV↔JSON and JSON↔XML. |
Good to know
- Replace source is ON by default — it overwrites originals with no backup. Turn it off in Settings › General to keep both.
- CSV has no types — every value is a string. Numbers and dates parse, but formatting, formulas and multiple sheets do not carry over.
- Non-standard delimiters or unusual encodings may need a check after conversion.
- The free plan processes 8 files per calendar day.
Tips
- For JSON data, JSON to CSV / CSV to JSON handle the row↔object mapping.
- After converting, the .xlsx opens with a real grid — no "Text to Columns" step needed.
- Combine several CSVs into one folder first if you want a batch of workbooks in one drop.
Frequently asked questions
Does it preserve formulas or formatting?
No — CSV is plain text, so there are no formulas, colors or multiple sheets to carry over. The conversion produces a clean data grid.
Can I go the other way?
Yes — the Excel to CSV tool converts an .xlsx back to .csv, taking the first sheet.
Is my data uploaded?
No — conversion uses the bundled xlsx library entirely on your device.
What about TSV or unusual delimiters?
The converter reads standard CSV. For TSV, the Power Tools category has a TSV↔CSV converter.