A paper sensor comprises a moveable grill. The paper sensor is arranged for location within an air flow in a printer, and comprises the grill as a paper-engaging body provided with a plurality of through holes such that air can flow freely through the grill. The grill is operable to move between a first position and a second position. The paper sensor is arranged so that in use a sheet of paper introduced adjacent the grill engages the grill and reduces the air flow through one or more of the holes in the grill, creating a pressure differential across the grill, that pressure differential causing the grill to move from the first position to the second position, and thereby indicating the presence of paper. A printer comprising a paper sensor, and a method of sensing paper is also disclosed.