See if you're running Linux, the world's best operating system.
Copyright (c) 2014–2016 Scott Zeid. Released under the X11 License.
https://amirunninglinux.com/
https://gnu.amirunninglinux.com/
https://gnu-plus.amirunninglinux.com/
Privacy Policy
This was made as a parody of Microsoft's now-defunct Windows 8.1 marketing site, amirunningxp.com. It's not foolproof, as it uses user agent detection, but it usually works, and it looks shiny, and it also has some informative text as to why Linux is good and how to get it. Written in PHP.
There's also an Android app, which obviously always answers yes and was intended as a joke.