This book is an open-access publication under a CC BY-NC 4.0 license. Fabian Pfaffenberger evaluates the scientific utility of Twitter by examining several common data collection and analysis methods. Twitter has become a popular source for studies, although the microblogging service is only partially suitable for research: limited representativeness, time-restricted data availability, and low data quality diminish its scientific utility. Nevertheless, Twitter is increasingly coming into focus in the scientific community due to its societal and media relevance, as well as the vast amount of freely available data.