Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for assisting the authoring of posts to an asymmetric social network. In one aspect, a method performed by a system of one or more data processing devices includes receiving, at the system, an identification of an electronic document that is available on the Internet, the system identifying image content in the electronic document, the system filtering the identified image content, the system triggering presentation of the filtered image content to an author of a post to an asymmetric social network, the system receiving a selection of a first image from amongst the presented image content, and the system adding the first image to a post to the asymmetric social network.