XLS to XLSM Converter

The XLS format utilizes the Binary Interchange File Format (BIFF) scheme, serving as the default spreadsheet standard for Microsoft Excel from versions 2.0 through 2003. Encapsulated within the Object Linking and Embedding (OLE) Compound File Binary Format (CFBF), XLS files store data in binary streams rather than XML. This proprietary structure supports formulas, Visual Basic for Applications (VBA) macros, and charts but lacks the compression efficiency and corruption resilience of the newer XML-based standards.

Microsoft Excel remains the primary software for full fidelity access to XLS files. On Windows and macOS, the operating system associates these files with the Office suite if installed. Alternatively, open-source solutions like LibreOffice Calc and Gnumeric provide robust reverse-engineered support for reading and editing XLS binaries on Linux and other platforms without requiring Microsoft licenses.

The XLSM format is a macro-enabled spreadsheet file created by Microsoft Excel 2007 and later versions, utilizing the Office Open XML (OOXML) standard (ISO/IEC 29500). Unlike the standard XLSX format, XLSM files store embedded macros written in Visual Basic for Applications (VBA), allowing for automation and complex scripting within the workbook. The file structure relies on ZIP compression to contain XML documents for data, styles, and macro binary parts (vbaProject.bin), presenting a security risk that often requires user authorization to execute active content.

XLSM files open natively in Microsoft Excel (2007+) on Windows and macOS, which provides full VBA execution support. For non-Microsoft environments, LibreOffice Calc, OpenOffice Calc, and WPS Office can open these files and view data, though VBA macro execution compatibility varies significantly. Google Sheets can import XLSM data but strips the VBA macros, converting the file to its native format without automation features.