The red-footed booby is the smallest member of the booby and gannet family at about in length and with a wingspan of up to . The average weight of 490 adults from Christmas Island was . It has red legs, and its bill and throat pouch are coloured pink and blue. This species has several morphs. In the white morph the plumage is mostly white (the head often tinged yellowish) and the flight feathers are black. The black-tailed white morph is similar, but with a black tail, and can easily be confused with the Nazca and masked boobies. The brown morph is overall brown. The white-tailed brown morph is similar, but has a white belly, rump, and tail. The white-headed and white-tailed brown morph has a mostly white body, tail and head, and brown wings and back. The morphs commonly breed together, but in most regions one or two morphs predominates; for example, at the Galápagos Islands, most belong to the brown morph, though the white morph also occurs.