Microsoft supports Office for the Windows and Mac platforms. Beginning with Mac Office 4.2, the Mac and Windows versions of Office share the same file format. Consequently, any Mac with Office 4.2 or later can read documents created with Office 4.2 for Windows or later, and vice-versa. Visual Basic for Applications support was dropped in Microsoft Office 2008 for Mac^[51] but was restored in Microsoft Office for Mac 2011.^[3]

There were efforts in the mid 1990s to port Office to RISC processors such as NEC / MIPS and IBM / PowerPC, but they met problems such as memory access being hampered by data structure alignment requirements. Microsoft Word 97 & Excel 97 however did ship for the DEC Alpha platform. Difficulties in porting Office may have been a factor in discontinuing Windows NT on non-Intel platforms.^{[citation needed]}

There is no mention of support for other operating systems, although Microsoft Office Mobile, which supports the more popular features of Microsoft Office, is available for Windows Mobile and is planned to soon be available for Symbian OS.

Crossover for Linux, by CodeWeavers, makes it possible to run Microsoft Office on the Linux platform. Doing so, however, requires a license for Microsoft Office for Windows, as well as a license for Crossover for Linux. Crossover is a computer code translation layer.