: Because of its long-standing history, .xls is often used as a "universal" format for transferring data between specialized software tools that may not yet fully support the .xlsx compression standards. .xls vs. .xlsx: Which Should You Use?
: Many older enterprise resource planning (ERP) systems or automated reporting tools still export data specifically in .xls format because the export logic was never updated to the newer XML standard.
: Some scientific journals still accept or even prefer supplemental data and tables to be uploaded in .xls or .csv formats for archival purposes. : Because of its long-standing history,
The file extension represents the legacy binary file format used by Microsoft Excel from its early versions until the release of Excel 2007. Known formally as the Excel Binary File Format (BIFF) , it served as the standard for spreadsheet data for nearly two decades, facilitating the storage of complex data, formulas, and formatting in a single compact file. Evolution of the .xls Format
While revolutionized by newer formats, .xls remains notable for its specific limitations compared to modern spreadsheets: : Many older enterprise resource planning (ERP) systems
The .xls format was the primary output for Excel versions 97 through 2003. Unlike its modern successor, the XML-based , the .xls format is a binary "container" that stores information in streams. This structure allowed for efficient data access but made the files more prone to corruption and harder for non-Microsoft applications to parse without specialized libraries like Apache POI . Key Technical Specifications
: Because it is a legacy format, almost all spreadsheet software—including Google Sheets , LibreOffice, and Apple Numbers—can still open and edit .xls files. Common Use Cases Today Known formally as the Excel Binary File Format
: The .xls format can contain VBA macros . However, because macros are embedded directly in the binary code, these files were historically used to spread macro viruses, leading to stricter security protocols in modern operating systems.
Despite being "outdated," .xls files are still frequently encountered in several professional contexts: