RetroArch can run on the usual platforms like Windows, Mac OS X and Linux, but it stands alone in that it can support far more platforms beyond just that.
We support operating systems that not even Microsoft and Apple themselves support anymore, such as macOS X on PowerPC Macs, and RetroArch being available on Windows OSes as far back as Windows 95.
On top of all that, RetroArch also runs on iOS and Android for tablets and phones, as well as on game consoles like PS2, PS3, PSP, PS Vita, Wii, Wii U, 2DS, 3DS, Switch, and more!
The current stable version is: 1.7.7
Note: OSX version for x86 32bit will return at a later point in time.