GroupLoop is a browser-based, collaborative audio feedback control system for musical performance. GroupLoop users send their microphone stream to other participants while simultaneously controlling the mix of other users’ streams played through their speakers. Collaborations among users can yield complex feedback loops where feedback paths overlap and interact. Users are able to shape the feedback sounds in real-time by adjusting delay, EQ, and gain, as well as manipulating the acoustics of their portion of the audio feedback path. This paper outlines the basic principles underlying Grouploop, describes its design and feature-set, and discusses observations of GroupLoop in performances. It concludes with a look at future research and refinement.