PolarScopEU proposes an original application, tailored for the context of different EU countries, that will measure and map, in two-dimensional spaces, the polarisation of their online social networks. This tool, to be made available first in Greece, Portugal and Spain, addresses not only the impact that online political communication, and misinformation, is having nowadays on democratic institutions, but also citizens’ unawareness of existing biases in the online political information that they are exposed to. More concretely, relying on automated analyses of Social Media content to assess politicisation levels of multiple key issues, this application will allow its users to: 1) better understand how they place, in terms of the online content that they create and consume, in two major dimensions of political content: diversity and bias; and 2) find out which actors are closer to them when it comes to the politicisation of several important issues (e.g., European Integration, Immigration, Environment). In order to create this application, the PolarScopEU will develop two additional products of extreme value for researchers and organisations to study, and monitor, online political communication. The first one is an innovative tool to measure, using alternative sources of text data, the levels of salience and contestation of different political issues. The second product is a periodically updated database, for each country, with polarisation and issue politicisation scores for an extensive list of national actors, including political parties, news media and other key opinion makers. These products will facilitate the comparison of issue politicisation across countries, time periods, and actors and originate an innovative polarisation index of online political communication in the EU countries.