A profile prediction system may identify one of multiple user profiles for a single computer. For example, a home computer may have multiple users that may not be targeted unless the user on the home computer can be identified. The system's user identification may be based on a clustering model that considers various browsing characteristics to identify different clusters that each correspond to a particular user or user profile. The model may be generated and refined by tracking web browsing over multiple sessions. Future activity on the computer may be used to identify which user is the source of the activity and the user may receive targeted content including advertisements.