This chapter presents a study designed to analyze the affordances and constraints of digital education platforms available for mathematics teachers. Analyses employ the theoretical lenses of both the documentational approach and connectivity. Three contrasting platforms (or cases) are compared across the European countries of Denmark, France and the Netherlands in terms of each platform’s potential instrumentation and instrumentalization processes for users and their micro- and macro-level connectivity. Results highlight important differences between these platforms. Such differences concern, in particular, the proposition of mathematical contents and/or of tools for designing lessons; the potential links with users’ resource systems; and the possibilities for collaboration, including the sharing of resources with colleagues. Furthermore, these differences seem to be strongly linked to national educational policies and national perspectives on teachers’ work. Finally, the study illustrates how the documentational approach and the concept of connectivity can be used to identify the potential consequences of digital platforms on teachers’ work.