This book contains two Open Access chapters. In an era where the digital landscape is increasingly marred by online hate, this groundbreaking book delves into this multifaceted world, offering an in-depth exploration of the origins, evolution, and impact of online hate material over the past decade. Supported by a robust series of quantitative analyses, Online Hate and Extremism draws on unique datasets collected from large, random samples of Internet users in the U.S. and Europe from a period of over a decade. Offering a comparative analysis across different countries, the chapters provide a broader understanding of cyberhate in various cultural contexts. Analysing both perpetrators and victims, the authors investigate who produces online hate material and why, as well as who is likely to be victimized and the consequences of such victimization. Offering practical insights, this insightful study also considers ways to reduce the spread of online hate and provides strategies to avoid being targeted. With timely data collection surrounding the 2024 U.S. presidential election, Online Hate and Extremism provides a snapshot of how current electoral politics influence the flow of online hate. By examining cyberhate cross-nationally and over time, this book offers a unique and essential perspective on one of the most pressing issues in the digital age.