CSV vs Excel: which format to use
What each format can hold, what gets lost in conversion, and when to choose which.
CSV and Excel files both store rows and columns, and Excel opens both, so they are easy to confuse. They are built for different jobs, and picking the wrong one causes most spreadsheet headaches.
What each format is
A CSV (comma-separated values) file is plain text: each line is a row, and commas separate the values. There is no formatting, no formulas, no sheets, no colours. Any program can read it, which is its whole point.
An Excel workbook (.xlsx) is a structured file that stores values, formulas, formatting, several sheets, charts, filters and data types. It is built for people working with data, and it needs spreadsheet software to open.
Side by side
| CSV | Excel (.xlsx) | |
|---|---|---|
| Formulas | No, only values | Yes |
| Formatting and colours | No | Yes |
| Several sheets | No, one table per file | Yes |
| Leading zeros and long numbers | Kept in the file, often lost when Excel opens it | Kept if stored as text |
| Opens in any program | Yes | Needs spreadsheet software |
| Accepted by import tools | Almost always | Sometimes |
| File size for large data | Small and simple | Compressed, handles formatting |
Use CSV when
- Importing into another system: mailing tools, CRMs, accounting software, online shops, databases.
- Handing data to a developer or a script.
- The data is one plain table and needs to open anywhere.
Convert a workbook with Excel to CSV, which exports each sheet as its own CSV and writes dates in a format every system reads.
Use Excel when
- People will read, edit, filter or chart the data.
- You need formulas, several sheets or formatting.
- The data has codes with leading zeros that must survive being opened.
Turn an export into a proper workbook with CSV to Excel, which keeps codes as text and detects the delimiter for you.
What gets lost when converting to CSV
Formulas become their current values, formatting disappears, and each sheet becomes a separate file. That is usually exactly what an import tool wants, but keep the original workbook if you will edit it again.
The European comma problem
In most of Europe the comma is the decimal separator, so Excel there saves CSVs with semicolons between values. A comma CSV then opens as one long column, and a semicolon CSV confuses import tools that expect commas. Both converters let you choose the delimiter, and CSV to Excel detects it automatically.
And JSON?
If the data is going into a website, an app or an automation tool, JSON is often what the developer wants. CSV to JSON turns the header row into property names.