Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for requesting audio only data for video content. One of the methods includes receiving, from a host server on a network, a plurality of content items, wherein a content item of the plurality of content items references video content. If device conditions, network conditions, or both, indicate that video data of the video content referenced by the content item should not be played on the user device, the user device requests only the audio data of the video content referenced by the content item and plays only the audio data on the user device.