A display device includes a display panel including a first display area and a second display area adjacent to the first display area, a processor configured to generate first image data corresponding to the first and second display areas for a first mode, and to generate second image data corresponding to the first display area for a second mode, and a display driver configured to drive the display panel in response to the first image data in the first mode, and to drive the display panel in response to the second image data in the second mode, wherein a supplementary image is displayed in at least a portion of the second display area in the second mode.