This book constitutes the refereed post publication proceedings of extended paper versions from the 20th International Conference on Web Information Systems and Technologies, WEBIST 2024, held in Porto, Portugal, during November 17–19, 2024. The 13 full papers and 4 short papers included in this book were carefully reviewed and selected from 69 submissions. They are organized in the following topical sections: Internet Technology; Web Intelligence and Semantic Web; Social Network Analytics; and HCI in Mobile Systems and Web Interfaces.