Twitch just updated its Terms of Service, and will no longer support streaming of games rated AO for Adults Only by the ESRB.
Before now, Twitch could ban specific games due to extreme sexual or violent content. But, as they wrote in a blog post on the subject, the process was “unsustainable and unclear, generating only further confusion among Twitch broadcasters. We would like to make this policy as transparent as possible…Simply put, AO games are not welcome on Twitch.”
The new policy won’t cover games rated 18+ by other ratings systems (like the European PEGI or Japanese CETA). However, any game that has been rated by the ESRB—a vast majority of games in the U.S.—will be subject to the the policy. Twitch also noted that specific games may still be banned based on content, and that includes games not rated by the ESRB.
It’s likely that the main reason for this focus on the ESRB is that 18+ ratings in other ratings systems are not equivalent to the ESRB’s AO rating. AO is a somewhat special designation that the ESRB assigns only to games that have extreme sexual or ultra-violent content. Only a tiny handful of games have ever received the AO rating; most recently, Hatred, which has players partake in a mass murder. Notably, most of these games get the Adults Only stamp for sexual content rather than violence. You can see the full list of AO games here.