Abstract: An online system stores information identifying interactions by online system users with an application provided by a third party system. The application includes a tracking mechanism specifying one or more interactions with the application. When a user performs a specified interaction with the application via a client device, the tracking mechanism communicates information describing the performed interaction from the client device to the online system. The online system stores interactions by the user with the application and generates one or more aggregations of interactions with the application that are communicated to the third party system. Each aggregation is associated with specific characteristics and identifies interactions by users having the specific characteristics with the application.

Abstract: An online system or third party system allows advertisers to evaluate and test ad creatives before the ad creatives are presented to users in an ad campaign. Based on a set of test ad creatives for which feature scores and objective scores are determined by content evaluators (e.g., users, content processing algorithms), a model is trained to determine objective scores for an ad creative based on feature scores of the ad creative. The trained model is applied to a target ad creative, which has yet to be or has been presented to users, to determine one or more objective scores for the target ad creative based on feature scores of the target ad creative. Feedback is presented to an advertiser associated with the target ad creative based on the objective scores determined for the target ad creative.