A display device includes a base substrate which includes a display area and a peripheral area, the peripheral area including a bending area; a first test signal line and a second test signal line which are located on the peripheral area; a lower insulating layer which is located on the first test signal line and the second test signal line; a first test connection pattern which is located on the lower insulating layer and connected to the first test signal line; a second test connection pattern which is located on the lower insulating layer, spaced apart from the first test connection pattern, and connected to the second test signal line; an upper insulating layer; and a first crack detection line which is located on the upper insulating layer, is connected to the first and second test connection patterns, and has at least a portion overlapping the bending area.