This handbook presents the state-of-the art scholarship on theoretical frames, mathematical content, learning environments, pedagogic practices, teacher professional learning, and policy issues related to the development and use of digital resources in mathematics education. With the advent of more and more open access digital resources, teachers choose from the web what they see fit for their classroom; students choose 'in the moment' what they need for their projects and learning paths. However, educators and students often find it difficult to choose from the abundance of materials on offer, as they are uncertain about their quality and beneficial use. It is clear that at a time of bouleversement of the teaching-learning processes, it is crucial to understand the quality and the (potentially) transformative aspects of digital resources. This book provides comprehensive analyses of and insights into the transformative aspects of digital resources.