What balance should be struck between freedom of expression, asan essential right and value of any democratic society, and other constitutionalrights when facing falsehood and extreme speech? Howare Europe and legislators around the world reacting to the rise ofonline disinformation and hate speech, in the wake of mounting evidenceof adverse effects on democratic processes? What is the mosteffective approach to address and tackle harmful practices over theInternet, if any? These are some of the pivotal questions that thisbook seeks to explore. The potentially global scale and the unprecedentedvelocity of the dissemination of false and extreme contentraise concerns that are specific to our digital age. It is the Authors'belief that the answers to such questions plunge their roots in theorigins of contemporary constitutionalism, with the paradigm ofthe constitutional traditions of Europe and the United States. Specifically, the right to freedom of expression, its development andsubsequent application to the digital dimension constitute the startingground of the analyses here proposed.