Massive open online courses (MOOCs) are one of the overarching topics of our times but have been subject to several controversial debates in recent years. Hitherto, the discussion has mainly focused either on some distinct success criteria for MOOCs, including technical features, enrolment numbers and dropout rates, or on the instructional dichotomy of xMOOCs and cMOOCs. With our article, we aim to shift the focus from the form to the content of MOOCs. Specifically, we address the questions of whether and, if yes, to what extent MOOCs are capable of enhancing students' knowledge of the topic at hand. We believe that MOOCs should be measured not only by the success rates of students passing the course but also by how they contribute to reaching specific learning outcomes conveyed by the course. Empirically, we use a mixed-method approach in which a quantitative survey is complemented with qualitative interviews to evaluate learning outcomes in a MOOC about climate change. Our results disclose that participation in the MOOC stimulated the learning of the students. MOOCs can therefore be understood as an educational tool for learning in various ways.