HTTP server log files provide Web site operators with substantial detail regarding the visitors to their sites. Interest ininterpreting this data has spawned an active market for software packages that summarize and analyze this data, providing histograms, pie graphs, and other charts summarizing usage patterns. While useful, these summaries obscureuseful information and restrict users to passive interpretation of static displays. Interactive visualizations can be used to provide users with greater abilities to interpret and explore web log data. Bycombining two-dimensional displays of thousands of individual access requests, color and size coding for additional attributes, and facilities for zooming and filtering, these visualizations provide capabilities for examining data that exceed those of traditional web log analysis tools.

We introduce a series of interactive visualizations that can be used to explore server data across various dimensions. Sample visualizations of server data from two web sites are presented. Coordinated, snap-together visualizations (STVs) of log data are introduced as a means of gaining additional expressive power. Possible uses of these visualizations are discussed, and difficulties of data collection, presentation, and interpretation are explored.