A large, long-winged, entirely gray-brown swiftlet with a very shallow tail fork and a gliding flight action. Found over a variety of habitats, often in flocks with other swiftlets. Almost always seen in flight. Widespread, so overlaps with multiple similar swiftlets. Uniform Swiftlet is larger and longer-winged than Glossy, Cave, and Bornean Swiftlets, with a dark belly and a non-fluttering flight action. Uniform Swiftlet lacks the clear pale rump of White-rumped, Seram, Halmahera, Sulawesi, and some Glossy Swiftlets, and is larger than those species. Uniform lacks gloss on upperparts, unlike Mayr’s, Mountain, and Glossy Swiftlets. It is smaller than Bare-legged, Mayr’s, Papuan, Volcano, and Giant Swiftlets. It is most similar to Edible-nest and Black-nest Swiftlets, but Uniform is darker beneath, and lacks the slightly paler rump of Edible-nest; it is best distinguished from those species by its mossy nest.