The book offers a theoretically grounded, but above all, practical guide to the professional use of RESTful HTTP. It describes the architectural style REST (Representational State Transfer) and its implementation within the protocols of the World Wide Web (HTTP, URIs, and others). It demonstrates how to design classic web applications and web services in accordance with the fundamental principles of the web and leverage its many advantages. After a brief introduction that conveys the basic principles (resources, representations, hyperlinks, content negotiation), a complete practical example is presented. Following that, the individual concepts as well as advanced topics such as caching, documentation, and security are examined in detail. Finally, an extended version of the example application is developed to implement the advanced concepts.