A sheet feeder includes a support to support a roll sheet winding a sheet, a sensor that is at a first position on the support and contacts a surface of the roll sheet to detect a level difference at a trailing edge of the roll sheet and output a first signal and a second signal, a roller that is at a second position different from the first position in a circumferential direction of the roll sheet on the support and contacts the surface of the roll sheet to guide the roll sheet, and circuitry to cause the roll sheet to rotate in a sheet feeding direction to feed the sheet, and detect the trailing edge of the roll sheet based on the first signal output from the sensor, and the second signal output from the sensor.