No serious attempt to answer the question 'What is hate speech?' would be complete without an exploration of the outer limits of the concept(s). This book critically examines both the ordinary and legal concepts of hate speech, contrasting social media platform content policies with national and international laws. It also explores a range of controversial grey area examples of hate speech. Part I focuses on the ordinary concept and looks at hybrid attacks, selective attacks, reverse attacks, righteous attacks, indirect attacks, identity attacks, existential denials, identity denials, identity miscategorisations, and identity appropriations. Part II concentrates on the legal concept. It considers how to distinguish between hate speech and hate crime, and examines the precarious position of denialism laws in national and international law. Together, the authors draw on conceptual analysis, doctrinal analysis, linguistic analysis, critical analysis, and diachronic analysis to map the new frontiers of the concepts of hate speech.