Social media are now central sites of democratic discourse among citizens. But are some contributions to social media too extreme to be permitted? This entry considers the permissibility of suppressing extreme speech on social media, such as terrorist propaganda and racist hate speech. It begins by considering the argument that such restrictions on speech would wrong democratic citizens, violating their freedom of expression. It proceeds to investigate the moral responsibilities of social media companies to suppress extreme speech, and whether these ought to be enforced through the law. Finally, it explores an alternative mechanism for combatting extreme speech on social media—counter-speech—and evaluates its prospects.