Extension Description Author File / Link
xls VB class to write an Excel BIFF 2.1 spreadsheet directly Paul Squires Download
OpenOffice.org's Documentation of the Microsoft Excel File Format Versions 2, 3, 4, 5, 95, 97, 2000, XP, 2003 Daniel Rentz Download
OLE Compound File (Structured Storage) format Deprecated resource Link
xlsx ZIP-packaged XML spreadsheet format (Microsoft Excel / ECMA-376 / ISO 29500) Microsoft / ECMA / ISO Link