Example techniques involve identification of device groups. In an example implementation, a mobile device displays, via a control application, a synchrony group control including controls to select playback devices for a synchrony group. The mobile device receives input data representing a command to create a new synchrony group, the input data including input data representing selection of two or more playback devices for a new synchrony group. In response, the mobile device forms the synchrony group by receiving input data indicating a particular group identification for the new synchrony group, determining that the particular group identification is unique among other synchrony groups, and sending data representing instructions to the playback devices to form the new synchrony group with the particular group identification. In response to forming the new synchrony group, the mobile device updates an interface for the media playback system to indicate the new synchrony group.