To obtain a printer in which use of a counterfeit of an ink ribbon or a roll of print medium can be inhibited, and to obtain a roll.

The printer includes a roll holding part which holds a roll constituted by winding a strip and to which an invisible identifier is imparted at the axial end thereof, an irradiation part which irradiates light toward the roll held at the roll holding part, a light receiving part which receives the light coming from a region of the roll including the identifier when light is irradiated from the irradiation part, an identification part which identifies the identifier based on the light reception results from the light receiving part, a control part configured to change a predetermined setting or operation or to perform a predetermined setting or operation according to the identification results from the identification part, and a print part configured to print on a print medium included in at least one strip.