In an electronic device capable of running multiple software applications concurrently, applications, documents, cards, or other activities can be selected for hibernation so as to free up system resources for other activities that are in active use. A determination is made as to which activities should hibernate, for example based on a determination as to which activities have not been used recently or based on relative resource usage. When an activity is to hibernate, its state is preserved on a storage medium such as a disk, so that the activity can later be revived in the same state and the user can continue with the same task that was being performed before the activity entered hibernation.