Inverse search systems and methods operate on identifiers of content items in a corpus such as the World Wide Web In an inverse search, the user submits a query that includes an identifier of a target content item in the corpus and receives information (metadata) about the target content item being returned to the user. Many types of metadata can be returned, including ratings or other metadata related to the target content item obtained from users, popularity data specific to the target content item, information about previously submitted forward search queries that led to the target content item being identified as a hit, and metadata extracted from the target content item.