The authors argue that humanitarian shelter responses should prioritize flexibility in order to accommodate diverse needs and capacities, particularly in the urban environment. The success of shelter assistance programs depends on: (1) flexibility (rather than adaptability); (2) invisibility of the final response within the urban landscape; and (3) virality, i.e. how well the program resonates and self-propagates. Flexibility is evident in shelter programs in Tacloban in the Philippines (‘shopping list’ of shelter typologies) and in Palu in Indonesia (cash grants and technical assistance to address community shelter needs through a range of diverse options). The authors identify several constraints on flexibility, including the ambition to engineer perfect shelter solutions and misconceptions of equity, which can limit the number of households assisted. Moreover, invisibility is constrained by the alignment of shelter programs with donor requirements, pre-set architectural/engineering notions of what is correct, mandates of implementing organizations, and responders’ other priorities.