A seemingly infinite and continuous stream of online content can be tracked by a movement tracker that can track an amount of movement of a stream of content. For example, such a movement tracker can track the amount of movement per session of a client-side application, such as per session of a web browser. In an example, the tracking of the movement can occur by tracking a measurable parameter of the stream that indicates the amount of movement, such as scroll distance. The movement tracker may also be configured to determine user interaction data according to the tracked amount of movement.