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Please predict whether this patent is acceptable.PATENT ABSTRACT: An online system receives a request from a user of the online system to generate a content item specifying content (e.g., an image) received from the user and one or more modifications to the appearance of the content to be included in the content item. The online system generates multiple instances of the content item based on the request, in which each instance includes a different set of the specified modifications. Using an identifier that identifies each instance based on the set of modifications to the appearance of the included content (e.g., using an image fingerprint), the online system tracks a performance metric associated with each instance. By comparing the performance metrics associated with the instances, the online system identifies one or more modifications responsible for one or more differences between the performance metrics and predicts an effect on the performance metrics associated with content item instances including the identified modifications.