The common goby has two dorsal fins with a narrow gap between them, the anterior one consisting of six to eight spines and the posterior one eight to eleven soft rays. The pelvic fins are fused. There are 39 to 51 scales along the lateral line and these scales are slightly larger than those of the sand goby (Pomatoschistus minutus). The caudal fin is rounded. In males, there is a conspicuous dark spot on the anterior dorsal fin and dark markings at the base of the pectorals and the caudal fin. Otherwise the colour is light grey or sandy brown with indistinct dark markings and dark striations on the pale fins. The colour of the male darkens during the breeding season and his fins become more coloured. The average size is about with a maximum of about
