The book "The Responsibilities of Online Service Providers" offers a comprehensive analysis of the responsibilities of online service providers (OSPs) in today's society. It highlights the complex and global challenges arising from the rapid development of internet services and resources. The authors, Mariarosaria Taddeo and Luciano Floridi, examine the role of significant players such as Facebook, Google, Twitter, and Yahoo, and their influence on the information environment as well as user interactions. The work addresses the responsibility of OSPs as information gatekeepers and their transformation from providers of connectivity and information services to platforms that offer open, free infrastructures and applications. Additionally, it discusses the ethical principles and guidelines that should govern the practices of OSPs, and it addresses users' rights as well as existing or lacking international regulations.