Over the past decade, the notion of mobility windows has become highly relevant for the European policy discourse and student mobility practices. In the current European policy context, mobility windows are mostly viewed as an instrument to achieve ambitious mobility targets in the Bologna context. However, despite the frequent use of the term and the associated hopes, no shared understanding of the concept of mobility windows has emerged in the European higher education community. What exactly are mobility windows? What makes them different from other types of international student mobility? Are there different types of mobility windows? How can mobility windows be integrated into study programmes? What is the impact and value of mobility windows for institutions and mobile students? These are some of the main questions explored in the present study. This publication was produced by the Academic Cooperation Association (ACA) in close cooperation with the Deutsches Zentrum für Hochschul- und Wissenschaftsforschung (DZHW) based in Germany and the Centre for International Mobility (CIMO) based in Finland. Financial support was granted by the European Commission. The study brings forward a new conceptual framework for the analysis of mobility windows and offers insight into the effective design and management of mobility windows.