What the converter does
A CSV file is plain text: rows on separate lines, values separated by commas. An Excel workbook is a structured file that knows which cells are numbers, how wide columns are and how values should display. The converter reads your CSV, decides carefully which values are real numbers, and writes an .xlsx workbook you can sort, filter, chart and total.
How to use it
- Choose your
.csvor.tsvfiles or drop them on the box above. - The separator and text encoding are detected automatically. The result note tells you what was found.
- Download the
.xlsxfile and open it in Excel, Google Sheets, Numbers or LibreOffice.
Numbers that stay correct
This is where most CSV imports go wrong. The converter stores a value as a number only when converting it can’t change it:
| In the CSV | In the workbook | Why |
|---|---|---|
1,234.50 |
Number 1234.5, shown as 1,234.50 | Safe to calculate with |
-12 or (45.00) |
Negative number | Accounting style is understood |
01067 |
Text 01067 |
A leading zero means an ID or postcode |
1234567890123456789 |
Text | Excel can’t store more than 15 digits exactly |
1.234,56 |
Text | European format; ambiguous without context |
2026-01-15 |
Text | Date formats differ between countries |
Columns are sized to fit their contents, so the workbook is readable the moment you open it.
Encodings and special characters
CSV files from older software are often saved in Windows-1252 rather than UTF-8, which is why accented names can turn into symbols like é when opened. The converter checks for UTF-8, UTF-16 and Windows-1252 and decodes each correctly, so Müller and Søren arrive intact. Quoted values with commas, quote marks or line breaks inside them are handled as the CSV standard (RFC 4180) describes.
Privacy
CSV exports are often customer lists, transactions or survey responses. Everything happens in your browser: the file is read with your device’s own text decoder and the workbook is written by SheetJS, an open-source library. Nothing is uploaded.
Questions
Why not just open the CSV in Excel?
Excel guesses the type of every value when it opens a CSV. It strips leading zeros from postcodes and IDs, rounds long numbers such as card or account numbers to 15 digits, and turns codes like 3-4 into dates. This converter only stores a value as a number when that's safe, so nothing gets changed.
Does it work with semicolon-separated files?
Yes. The separator (comma, semicolon, tab or pipe) is detected from the file, so CSVs exported in European formats work without any settings.
Are dates converted into Excel dates?
No. Dates stay as text exactly as written, because a value like 03/04/2026 means different days in different countries, and guessing wrong silently corrupts data. You can convert them in Excel with Data › Text to Columns if you need date arithmetic.
How big a CSV can it handle?
Excel sheets hold up to 1,048,576 rows. Files of tens of megabytes convert fine on a computer; on a phone, very large files may run out of memory.
Last reviewed 3 November 2026