Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for generating action trails from web history are described. In one aspect, a method includes receiving a web content access history of a user, the content access history including one or more user actions, each user action being associated with a content item upon which the user action is performed and identifying one or more action trails from the content access history, each action trail including a sequence of user actions performed one content items relating to a topic. Identifying a particular action trail includes clustering the user actions into a series of segments using temporal criteria; calculating semantic similarities between the content items, and adding a segment of the series of segments to the action trail when the semantic similarities between the segment and another segment satisfy a similarity threshold.