What is CSV?
CSV is the simplest way to store tabular data: each line is a row and commas separate the columns. It is plain text, opens in Excel, Google Sheets and any programming language, and is the universal format for exporting and importing spreadsheets and databases.
What is XLSX?
XLSX is the modern Microsoft Excel spreadsheet format. It stores multiple sheets, formulas, formatting and charts in a compressed XML package, and is the standard for sharing rich spreadsheets that go beyond plain CSV.
CSV vs XLSX: how they compare
Both formats have their place. This table summarises the practical differences so you can pick the right one for the job.
| CSV | XLSX | |
|---|---|---|
| Format type | Data | Data |
| Compression | None | Zipped XML |
| Quality | Lossless | Lossless |
| Best for | Spreadsheet exports and imports | Rich spreadsheets with formulas |
Why convert CSV to XLSX?
Converting CSV to XLSX gives you a file that is better suited to rich spreadsheets with formulas and financial models and reports, and that opens it up to far more apps, devices and websites.
What XLSX gives you: formulas, formatting and charts, multiple sheets in one file and opens in Excel, Sheets and LibreOffice.
Where CSV falls short: no data types — everything is text, no support for nested data and delimiter and encoding ambiguity. Converting keeps your content while moving to a format that matches where the file is going.
Tips for the best results
- XLSX is lossless, so your converted files keep every detail of the original CSV.
- You can convert several files in one go — add as many CSV files as you like and download them together.
- Everything runs locally in your browser, so even large files convert quickly and nothing is uploaded.