Twitch implemented a new ‘Activity Sharing’ integration with the popular Friends feature. Activity Sharing lets users easily share what you’re watching or streaming with all your Twitch friends.
Activity Sharing with friends has already made Twitch more social because users are discovering new channels, forming more friendships, and friends are watching streams together more than ever.
Activity Sharing now lets users know which of their friends are already watching the same stream or when a new friend joins the channel.
For those of you who do not want to share their activity, they can hide Activity Sharing by clicking on the status under your username and untick the checkbox.
via Twitch Blog