Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for content presentation. In one aspect, a method includes receiving a request for sponsored content; determining a sponsored content item to provide in response to the request, the sponsored content item being associated with a particular application; providing the sponsored content item for display on a user device; receiving data indicating that the sponsored content item has been selected on the user device; generating and returning a cookie to the user device, the cookie including a cookie identifier associated with the sponsored content item; receiving the cookie identifier in response to a user launch of the application; and logging a conversion event for the sponsored content item using the cookie identifier.