This book constitutes revised selected papers from the 15th International Conference on Web Information Systems and Technologies, WEBIST 20109 held in Vienna, Austria, in September 2019. The 10 full papers presented in this volume were carefully reviewed and selected from originally 87 paper submissions. They contribute to the understanding of relevant trends of current research on Web Information Systems and Technologies, including Big Data and Connected Services; Web Performance; Context-aware and Adaptive Web Applications; Human Robot Collaboration and Multi-Agent Systems; Web Application Operating Systems and Platforms; Social Media Advertising and Enhancing Purchase Intentions; Natural Language Query Interfaces and Semantic Web; and Human-computer Interaction and Dynamic Web Pages.