Developer tool / 08
CSV to Excel Converter
Turn CSV text into a real .xlsx workbook, without uploading the data.
CSV to Excel Converter: TOEA reads the CSV with a quote-aware parser and writes a genuine xlsx workbook, keeping numbers numeric while leaving identifiers such as postcodes as text. Runs 100% locally in your browser with zero server file uploads.
- Category
- Developer tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
Up to 5 MB · nothing is uploaded
Numbers Excel cannot hold exactly
Excel stores numbers with 15 significant digits. A digits-only value longer than that, such as a card number, an order reference, or a 64-bit ID, is written as a number and comes out rounded, often shown as 1.23457E+18. Values with thousands separators, currency symbols, or decimal commas, like 1,234.50 or €5, are not recognised as numbers and land as text, so sums skip them. Clean those columns in the CSV first, or prefix long IDs with a letter so they stay text.
Dates, formulas, and the input file
Dates are written as text, so 2024-03-01 sorts correctly but date arithmetic will not work until the column is converted with Excel's Text to Columns or DATEVALUE. A cell starting with = is also stored as text rather than as a formula, which keeps untrusted data from running when the workbook is opened.
The input must be comma-separated. A file exported with semicolons ends up in a single column; check the split first in the CSV viewer. One worksheet holds at most 1,048,576 rows.
How to use it
- Paste CSV or choose a file.
- Check the row count.
- Download the workbook.
Privacy & limitations
The text is converted in your browser and never uploaded, which matters when the file is a config or an export you would rather not hand to a stranger. The workbook is assembled in your browser from the browser's own compression, so no spreadsheet library is loaded.
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Frequently asked questions
Why not just rename the file to .xlsx?
That does not work — xlsx is a zipped bundle of XML, not delimited text. Spreadsheets refuse the file or show one column of raw commas.
Will my leading zeros survive?
Yes. A value like 01234 is written as text so it stays 01234, rather than becoming the number 1234 the way a plain CSV import often does.
Are numbers still numeric?
Yes. Anything that reads as a plain number is written as one, so sums and charts work without re-typing the column.
Can I control the sheet name?
It is taken from the file name you loaded, trimmed to what Excel allows.
Free tool · runs in your browser · no account required