XLSX vs XLS
How do XLSX and XLScompare? Here's everything you need to know to choose the right format — and how to convert between them.
.xlsx
Full guide →Office Open XML Spreadsheet
XLSX is the default format for Microsoft Excel spreadsheets. It supports complex formulas, charts, pivot tables, and large datasets. It's the industry standard for data analysis and financial modeling.
.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 While superseded by XLSX, many existing spreadsheets and enterprise systems still use this format.
| Specification | XLSX | XLS |
|---|---|---|
| Full name | Office Open XML Spreadsheet | Microsoft Excel Spreadsheet (Legacy) |
| Extension | .xlsx | .xls |
| MIME type | application/vnd.openxmlformats-officedocument.spreadsheetml.sheet | application/vnd.ms-excel |
| Category | Document | Document |
| Developer | Microsoft | Microsoft |
| Year introduced | 2007 | 1987 |
XLSX advantages
- Powerful formula and calculation engine
- Supports charts, pivot tables, and macros
- Industry standard for business data
- Compatible with Google Sheets and LibreOffice
XLSX limitations
- Complex format for simple data
- Can be slow with very large datasets
- Formatting issues between applications
- Requires office software for full features
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
Which should you use?
XLSX and XLS serve different purposes. XLSX is ideal for financial reports and budgets, while XLS excels at legacy spreadsheet compatibility.
Best uses for XLSX
Best uses for XLS
Convert between XLSX and XLS
Need to switch formats? Convert for free with SquishConvert.