The common firecrest is a small plump bird, 9 cm in length with a wingspan of 13–16 cm and weighs 4–7 grams. It has bright olive-green upperparts with a bronze-coloured patch on each shoulder, and whitish underparts washed with brownish-grey on the breast and flanks. The contact call is three or four thin high notes, similar to that of goldcrest, but slightly lower in pitch, zit-zit-zit rather than see-see-see.