A CSV file is plain text in which values are separated by commas (or semicolons); an XLSX file is Excel's native format, which beyond the data keeps formatting, formulas, multiple sheets and data types. Converting from CSV to XLSX is needed when raw data has to become a full worksheet. The converter above does the transformation in the browser; below you'll find the concrete differences and the mistakes to avoid.
CSV and XLSX: differences that matter
- CSV: plain text, lightweight, universal, but with no formatting, formulas or multiple sheets. Each line is a row of data, each value is separated by a delimiter.
- XLSX: a compressed archive that stores cells, styles, formulas, charts and multiple sheets. It's richer but specific to Excel and compatible spreadsheets.
How to convert
Upload the CSV file: the tool reads rows and columns and generates an .xlsx file with the data laid out in cells, ready to open in Excel, LibreOffice Calc or Google Sheets. From that moment you can apply formatting, formulas and filters that the CSV could not hold.
When you really need it
- When you have to add formulas or pivot tables to data exported from a management system in CSV.
- When you need formatting (colours, column widths, frozen headers) that CSV doesn't save.
- When you want to merge several tables into different sheets of the same file.
Common problems (and how to avoid them)
- Wrong separator: in many European locales Excel uses the semicolon as a separator. If all columns end up in a single cell, the CSV uses the comma where the semicolon is expected (or vice versa).
- Lost leading zeros: postal codes and codes like "00123" can become "123". In XLSX you fix this by setting the column as text.
- Corrupted accented characters: this depends on the encoding. A CSV saved in UTF-8 prevents "città" from becoming "città ".
Example: from a system export to a report
Many management systems and CRMs export data as CSV. By converting it to XLSX you get a sheet where you can add a column with a formula — for example =B2*1.22 to compute the VAT-inclusive amount — apply filters on the headers and format amounts as currency. Operations impossible in CSV, which keeps only the raw values with no formulas or formatting.
CSV or XLSX: which to choose
Use CSV when you only need to exchange raw data between different programs, import into a database or handle very light files. Use XLSX when the file has to be read and worked on by a person in Excel: formulas, charts, multiple sheets, formatting and typed columns. In short: CSV for data portability, XLSX for spreadsheet work.
Checking after conversion
After converting, it's worth checking three things: that the columns are separated correctly (and not all in one), that postal codes and codes with leading zeros are intact, and that accented letters are correct. If something is off, the cause is almost always in the source CSV — separator or encoding — rather than in the conversion itself.