Citizen science (CS) is a set of practices for organizing scientific research in a wide range of thematic areas using volunteers at various stages of the research process, them being not professional scientists. The article analyzes the activities of foreign libraries in order to implement CS projects. Both academic, research and public libraries abroad are involved in CS. Libraries (as well as archives and museums) are implementing crowdsourcing projects to create digital collections. Libraries help their readers who have decided to become volunteers navigate CS information resources on the Internet; create on their websites guidelines for using the necessary equipment and software to carry out CS projects; advertise, discuss, visualize and place in repositories the data collected by volunteers for such projects.