A display device having high visibility regardless of illuminance of external light is provided. A display device with reduced power consumption is provided. The display device includes a first light-receiving circuit including a first light-receiving element; and a pixel circuit including a display element. The first light-receiving circuit and the pixel circuit are formed over the same substrate. The gray level of the display element is changed according to a change in the amount of light to which the first light-receiving element is exposed. In particular, the gray level of the display element is decreased with a decrease in the amount of light exposure.