RETRIEVING SUPPLEMENTAL CONTENT

A system may provide supplemental content to a viewer of a content item through use of an embedded identifier indicating an address of associated supplemental content identifying data. The supplemental content identifying data may identify one or more supplemental content items associated with the content item and available to the viewer. An address or other identifier in the supplemental content identifying data may be used to retrieve at least a portion of the available supplemental content items, and a display may be generated combining the content item with the supplemental content. In some embodiments, the identifier may be securely provided to a client and may be authenticated as part of retrieving supplemental content associated with the content item. The identifier may comprise a trusted token or security token used to authenticate the supplemental content identifying data associated with the content item.