In one embodiment, a method includes providing a variant user interface to a first subset of a plurality of user devices, wherein the variant user interface is based on baseline user activity data indicative of user activities associated with a baseline user interface provided to the plurality of user devices, obtaining variant user activity data indicative of user activities associated with the variant user interface, and generating, based on the variant user activity data, effect data indicative of an effect of the variant user interface on one or more of the user activities.