This book constitutes the refereed proceedings of the 13th International Conference on Web Engineering, ICWE 2013, held in Aalborg, Denmark, in July 2013. The 21 full research papers, 4 industry papers, and 11 short papers presented were carefully reviewed and selected from 92 submissions. The scientific program was completed with 7 workshops, 6 demonstrations and posters. The papers cover a wide spectrum of topics, such as, among others: web mining and knowledge extraction, semantic and linked data management, crawling and web research, model-driven web engineering, component-based web engineering, Rich Internet Applications (RIAs) and client-side programming, web services, and end-user development.