Ferreira is primarily a synth-pop singer, also being described as dance-pop, indie pop,indie rock, alternative rock, and art pop. Her earlier work incorporated elements of dance-pop and electropop, most notably seen in tracks from As If! and Ghost.The latter EP also includes elements of acoustic and new wave. Her lyrical content originally incorporated themes of rebellion and teenage romance; Andrew Unterberger from Popdust opined that “17” plays the girl-gone-wild tale as a near-horror story, clearly meant to shock and upset", while noting that “One” "instead features a robo’d out Sky bemoaning the breakdown of connection in a relationship, and her own inability to feel anything as a result."As her career progressed, Ferreira more frequently experimented with elements of indie rock, which were commonly heard in her first album Night Time, My Time.Ferreira’s vocal range has been described as that of a contralto.