Maritime transport accounts for a majority of trades in volume, of which 70% in value is carried by container ships that transit regular routes on ﬁxed schedules in the ocean. In the present paper, we analyse a data set of global liner shipping as a network of ports. In particular, we construct the network of the ports as the one-mode projection of a bipartite network composed of ports and ship routes. Like other transportation networks, global liner shipping networks may have core-periphery structure, where a core and a periphery are groups of densely and sparsely interconnected nodes, respectively. Core-periphery structure may have practical implications for understanding the robustness, eﬃciency and uneven development of international transportation systems. We develop an algorithm to detect core-periphery pairs in a network, which allows one to ﬁnd core and peripheral nodes on diﬀerent scales and uses a conﬁguration model that accounts for the fact that the network is obtained by the one-mode projection of a bipartite network. We also found that most ports are core (as opposed to peripheral) ports and that ports in some countries in Europe, America and Asia belong to a global core-periphery pair across diﬀerent scales, whereas ports in other countries do not.