Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for dynamically selecting a content loading technique are disclosed. In one aspect, a method includes the actions of receiving a request for third-party content. The actions further include generating a first loading score that reflects a likelihood that a third-party content item that is selected using the first third-party content loading technique will render on a display of the client device. The actions further include generating a second loading score that reflects a likelihood that a third-party content item that is selected using the second third-party content loading technique will render on the display. The actions further include comparing the first and second loading scores. The actions further include selecting the first third-party content loading technique. The actions further include selecting and providing a given third-party content item.