• The current Web is characterized by global information overload and repetitive searching and browsing using Google.• Debates about Web 3.0 are still somewhat theoretical, but a common theme is “developing an integrated web of data” based on sound principles of information systems design. Some experts say that the principles of librarianship should play a role in improving how the Web is organized.• In 2008, semantic technologies are being used to solve information retrieval problems in bioinformatics, which may have specific applications in medicine. The term “Semantic Web” is occasionally used as a synonym for Web 3.0 (and vice versa), though some disagree with that usage.• Health librarians should be thinking ahead about how to design better domain-specific search tools and user experiences (including virtual) in Web 3.0.