If your friends are having trouble seeing one of these Hangouts apps, make sure they have added the app by clicking on the Apps tab in the lower left of your Hangouts window. Also, Hangouts apps are not yet supported on mobile devices. For optimum viewing, we recommend a recent browser on a recent Mac, Windows, or Chrome operating system, on a fast connection.

For those who prefer to geek out on the above, please see the full system requirements for Hangouts.