A large swift with long pointed wings and a long, deeply forked tail. It has black upperparts, tail, and wings, with a prominent white rump. Feathers of underparts broadly fringed with dirty white, and throat is whitish. Often difficult or nearly impossible to separate in the field from other similar “fork-tailed swifts,” but the white rump band is slightly thinner than that of Pacific Swift, while Salim Ali’s Swift has a slightly differently shaped white throat patch. This species is less blackish than Cook’s Swift, with a slightly wider rump band. Mostly sticks to hills while breeding, but disperses widely post-breeding and large flocks or loose individuals can be seen almost anywhere.