A copolymer includes a repeating unit of Formula (I) and a repeating unit of Formula (II), a composition includes the copolymer, and an optical film has a layer formed of the composition, in the Formulae (I) and (II), R1 and R2 represent a hydrogen atom or an alkyl group, L3 and L1 represent a divalent linking group, L2 represents a single bond or a divalent linking group, and L4 represents a single bond or a divalent linking group, L4 does not represent a linking group including —O(C═O)—NH—, X represents a perfluoropolyether group, an alkyl group having a branched structure in which hydrogen is all substituted into fluorine, an alkenyl group, or an alkynyl group, and Y represents a crosslinking group.