Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for joint distribution of content by multiple publishers. In one aspect, a method performed by one or more computers includes receiving data from a first content publisher, as well as accessing a publisher database that indicates information about other content publishers. A first set of candidate publishers is selected based on compatibility with characteristics specified by the first content publisher. A second set of candidate publishing partners is selected, as a subset of the first set of candidate publishing partners, based on compatibility of the first content publisher with characteristics specified by the candidate publishing partners. One of the content publishers in the second set of candidate publishing partners is selected, and a jointly published content item that references both the first content publisher and the selected publishing partner is provided for presentation to content recipients.