Format comparison
XLS vs CSV
How do XLS and CSVcompare? Here's everything you need to know to choose the right format — and how to convert between them.
.xls
Full guide →Microsoft Excel Spreadsheet (Legacy)
XLS is the legacy binary format used by Microsoft Excel before 2007. While superseded by XLSX, many existing spreadsheets and enterprise systems still use this format.
.csv
Full guide →Comma-Separated Values
CSV is the simplest tabular data format — rows of values separated by commas. It's the universal exchange format for data between databases, spreadsheets, and programming languages.
| Specification | XLS | CSV |
|---|---|---|
| Full name | Microsoft Excel Spreadsheet (Legacy) | Comma-Separated Values |
| Extension | .xls | .csv |
| MIME type | application/vnd.ms-excel | text/csv |
| Category | Document | Document |
| Developer | Microsoft | IBM (original concept) |
| Year introduced | 1987 | 1972 |
XLS advantages
- Compatible with older Excel versions
- Widely recognized format
- Supported by all major spreadsheet apps
- Large installed base
XLS limitations
- Limited to 65,536 rows and 256 columns
- Larger file sizes than XLSX
- Binary format — harder to recover
- Missing modern Excel features
CSV advantages
- Universal data exchange format
- Human-readable plain text
- Tiny file sizes
- Supported by every data tool
CSV limitations
- No formatting or styling
- No data types — everything is text
- Encoding and delimiter issues common
- No support for multiple sheets or formulas
Which should you use?
XLS and CSV serve different purposes. XLS is ideal for legacy spreadsheet compatibility, while CSV excels at data import and export.
Best uses for XLS
Legacy spreadsheet compatibility
Older enterprise systems
Historical data archives
Backward-compatible exports
Best uses for CSV
Data import and export
Database migrations
API data exchange
Data science and analysis pipelines
Convert between XLS and CSV
Need to switch formats? Convert for free with SquishConvert.