The rise of online hate speech has been fuelled in several countries by political polarisation and the growth of the alt-right movement. While this form of hate speech is not a criminal offence, it has serious psychological and social consequences for vulnerable target groups. There is no universally accepted definition of hate speech, but some indicators can be identified, including sexist language, denial of human rights, incitement to violence and negative stereotyping of minorities. Hate speech relies on simplistic explanations and discursive strategies that promote group inclusion/exclusion and antagonism. They are rooted in contemporary populist movements and can lead to stochastic terrorism. These can also affect public opinion, shift the Overton Window of acceptable Political Possibility, and influence the media agenda. While authorities, journalists, cultural actors, and citizens are all involved in combating hate speech, this raises a debate about freedom of expression