Globally, along sandy coastlines, foredunes support ecosystem services including provision of habitat and protection of communities from waves and storm surge. In this Review, we discuss the interactions between sand transport and vegetation processes (ecomorphodynamics) that give rise to the foredune-building feedback as illuminated by empirical and modelling studies. Foredune shape and alongshore continuity depend primarily on sand supply, vegetation density and growth form. For instance, low-lying, creeping herbaceous species tend to form short embryo dunes, whereas tall, dense grasses that grow vertically tend to form tall, narrow foredunes. Climate and weather events, herbivory and anthropogenic disturbances of varying scale affect the foredune-building feedback. For example, small local scale disturbances, such as herbivory or trampling, cause local vegetation loss and erosion. Management activities, such as beach nourishment, can increase foredune sand supply, leading to foredune rebuilding, although the presence of infrastructure on the back beach can inhibit foredune development. At a regional scale, hurricanes and tropical storms cause substantial dune erosion and overwash, potentially resetting the foredune-building process. Sea-level rise exacerbates the effects of storms, leading to increased erosion, saltwater intrusion and a potential landward shift in foredune location. Future research should prioritize integrated ecomorphodynamic observations and modelling to fill critical knowledge gaps and address the effects of changing climate on the foredune-building process.