Recent technological innovations in open source software and cloud computing have driven the cost of launching a software startup down to a fraction of what it was only few years ago. But as software products increasingly live in the cloud and rely on ongoing customer relationships to be profitable, understanding what drives long-term user engagement is paramount. The objective of this thesis is to shed light on this topic by answering the research question “How can user engagement be increased in SaaS and Social products?” Through a multidisciplinary literature review and an exploratory thematic analysis of seven software startups with SaaS and Social products (e.g. social media, communities, social games), an integrated model for increasing user engagement in such products is developed. Although there are differences observed between SaaS and Social products, they are limited to a few areas such as network effects and the importance of a reliable service, rendering any effort to develop two separate models unavailing. It is demonstrated that various measures aimed at increasing ability, motivation, and triggers are central in increasing engagement, but also that they vary throughout a user’s relationship with a product. Some recurring and important measures identified include an effective onboarding process, timing of triggers, storing value, integrating with key industry players to reduce lock-in, and using data in unique ways. From these findings, a three-stage model, consisting of activation, manual retention, and automatic retention, is proposed. More research and experimentation is needed to empirically verifying the proposed model – and yet it is not unlikely that the findings are relevant to other online and digital services requiring ongoing usage. Finally, practitioners attempting to implement the findings should do so in a responsible manner, without exploiting their users. Additional appendices can be requested from https://thomas.do/thesis/