Web usage mining, the analysis of user navigation paths through web sites, is a common technique for evaluating site designs or adaptive hypermedia techniques. However, often it is hard to relate aggregated clusters or measures to actual user navigation behavior. By contrast, basic graph-based visualizations of user navigation paths are easier to interpret, but it is difficult to find effective views that convey all the required information. In this paper we present the Navigation Visualizer, a web usage analysis tool that combines the two approaches. The Navigation Visualizer makes use of the rich data set that is collected by the Scone proxy-based web enhancement framework and facilitates dynamic selection of the data and interactive exploration with various layout mechanisms, color codings and markers. Several aggregated measures can be calculated and exported to statistical and data mining packages. Author Keywords User navigation, web sites, access tracking, interactive visualiza...