Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for switching display modes based on connections between devices. In one aspect, it is determined that an external display has been connected to or disconnected from a mobile device. Based on the determining, an application executing on the mobile device is switched between a first display mode and a second display mode. In the first display mode, a single user interface is displayed on the touch screen of the mobile device. In the second display mode, a first user interface is displayed on the external display and a second user interface, for receiving user inputs, is displayed on the touch screen of the mobile device.