The AT Internet tracking is used as an SKO certified measurment of ratings in terms of audience size and engagement. The AT Internet measurements are implemented both via the NPO Tag on NPO Start/Plus, but also on other domains belonging to Public Broadcasting. As such, AT Internet is the most widely implemented measurement of Public Broadcasting online performance. Unfortunately, the AT Internet tag does not support more fine-grained measurements, such as offers and choices of content. For this reason, the Topspin (divolte) tracker is used.