The pale crag martin of the nominate subspecies "P. o. obsoleta" is 12–13 cm (4.7–5.1 in) long with light brown upperparts, becoming paler on the lower back, and a short square tail that has small white patches near the tips of all but the central and outermost pairs of feathers. It has a pale grey throat, upper breast and underwing coverts, and the rest of the underparts are a dirty white. The eyes are brown, the small bill is mainly black, and the legs are brownish-pink. The wing length averages 1.3 cm (4.55 in) and the tail averages 4.8 cm (1.9 in). The sexes are similar in appearance, but juveniles have pale edges to the upperparts and flight feathers. The other subspecies differ from the nominate form as detailed in the table above.