All recent desktop versions of Microsoft Excel for Windows are supported, including Office 365. The minimum supported version of Excel is Excel 2003, though some features require Excel 2007.
Both 32-bit (x86) and 64-bit (x64) versions of Excel are supported. Note that the first 64 bit version of Excel was Excel 2010, and prior to that only 32-bit versions of Excel are available.
The minimum supported version of Windows is Microsoft Windows XP.
PyXLL is not available for Microsoft Excel for Mac (macOS or OS X) or the online (web) version of Office 365.
Other spreadsheet software such as OpenOffice, LibreOffice and Google Docs are not supported.