Critics praised "Who Is It" as exuberant and catchy. It peaked in the top five on the single charts in Spain and reached the top 30 in Italy and the United Kingdom. The music video was directed by Dawn Shadforth and shot outdoors in Iceland, and features Björk in a bell-shaped dress designed by Alexander McQueen. During the promotional campaign for "Medúlla", Björk performed the song on a number of occasions, such as "Friday Night with Jonathan Ross" and "L'Album de la semaine". She performed it on subsequent tours. It has been covered by Bon Iver and Kurt Elling.