In all seasons, the plumage is dominated by a harlequin-like pattern of black and white. Breeding birds have reddish-brown upper parts with black markings. The head is mainly white with black streaks on the crown and a black pattern on the face. The breast is mainly black apart from a white patch on the sides. The rest of the underparts are white. In flight it reveals a white wingbar, white patch near the base of the wing and white lower back, rump and tail with dark bands on the uppertail-coverts and near the tip of the tail. The female is slightly duller than the male and has a browner head with more streaking.
The Sanderling breeds in the High Arctic areas of North America, Europe and Asia. In North America, it breeds in the Canadian Arctic Archipelago, Nunavut, Greenland (and to a lesser extent Alaska). In Eurasia, it breeds in Spitsbergen and areas of northern Russia from the Taymyr Peninsula to the New Siberian Islands. In the northern winter, it has a nearly cosmopolitan distribution across the world’s marine coasts. It is a complete migrant, travelling between 3,000 to 10,000 km (1,900 to 6,200 mi) from its breeding grounds to its wintering sites. Birds that travel further also arrive later and leave sooner. Most adults leave the breeding grounds in July and early August, whereas juvenile birds leave in late August and early September. The northward migration begins in March at the southern end of their winter distribution.