If someone posts a death threat or a violent manifesto online, will they cross over from words to deeds? Explicit threats, intimidation campaigns, and incitements to violence are no rarity among white nationalists, incels, and other racist and misogynist extremists. Yet it is often difficult to determine whether they pose genuine risks, since the boundaries between trolling and true violent intent can be blurry. How can we tell the difference between online bluster and terrorist threats?

Julia Ebner—an internationally acclaimed expert on online radicalization—offers a fresh approach, showing how language patterns reveal the potential for political violence. She investigates the psychological underpinnings of texts by terrorists such as Anders Breivik, Dylann Roof, Elliot Rodger, and Brenton Tarrant, offering statistical and qualitative contrasts with nonviolent political writing. Ebner finds striking similarities among their manifestos, including the fusion of personal identity with the group, visceral othering of outgroups, narratives of existential conflict, and the glorification of violence. Following these trails, she demonstrates that perpetrators of extremist violence inadvertently give away their intentions in what they say. Featuring vivid writing and actionable conclusions, The Language of Terrorists presents a new model of violent threat detection that can address pressing challenges faced by the international security and intelligence communities.

Julia Ebner is the leader of the Violent Extremism Lab at the University of Oxford’s Centre for the Study of Social Cohesion and co–executive director at the Institute for Strategic Dialogue. She regularly advises governments, intelligence agencies, tech firms, and international organizations. Her books include Going Dark: The Secret Social Lives of Extremists (2019) and Going Mainstream: How Extremists Are Taking Over (2023).