Hundreds of millions of comments, posts and tweets are left everyday by people all over the world, but many of them are polarized and uncivil, clearly stretching freedom of speech and often putting democratic political debate into question. Different social and political actors are also using the online media environment to propagate ideas, set agendas, manipulate news frames, or simply to disrupt and shock. This research is aimed at understanding attitudes and behaviours towards offensive language, hate messages, message/news distortion, and polarization of issues, and how these impact on the quality of political debate (and ultimately on the quality of democracies). The approach is comparative and includes several countries and different online environments. Investigating these issues in different countries and in different online environments allows a comprehensive understanding of the conditions that propitiate verbal violence and the distortion of information. The proposal addresses these pressing issues and the impact of technology on society, through a comparative and innovative multi-methods and interdisciplinary approach. The research team includes national and international researchers from the fields of political science, social psychology, information and computer science, media studies, communication, and sociology based at the ICS-UL and at the INESC-ID, which complement each other both regarding the research topics and the methodological approach. The project has therefore strong innovative potential to impact both on research and on society and to inform and interest the research community, but also policy-makers and the wider public that is increasingly dependent on the Internet.