The article presents a framework for mapping digital communication systems and thereby analyzing how and why structural conditions differ across national contexts. Following the ‘turn to infrastructure’ in internet studies, we conceptualize communication systems as made up by infrastructural, market and policy structures that enable and constrain mediated communication in a given society. As opposed to media system analyses that typically focus on legacy media institutions, we take individual internet users as our theoretical point of departure and ask how their communicative capabilities are regulated. In order to exemplify the application of the framework, we describe the methodological steps in a mapping of the components of the Danish communication system. In conclusion, we discuss the overall findings that the method uncovers and its implications for future comparative research.