Content provider systems publish content via content publishing platforms. An online system is associated with multiple content publishing platforms. Each content publishing platform is associated with policies that determine whether a content item is acceptable for publishing via the content publishing platform. For example, the policy may specify dimensions of a media object of the content item, keywords that are unacceptable for publishing via the content publishing platform, and so on. The online system receives requests from content provider systems to publish content via a particular content publishing platform. The online system determines whether the content item is suitable for publishing via one or more other content publishing platforms. The online system determines whether the content provider system approves publishing content via any of the identified content publishing platforms. The online system may deliver the content item to all content publishing platforms approved by the content provider system.