Online Rabbit Holes and Radicalization. Algorithmic Pathways, Fringe Networks, and the Digital History of Extremist Recruitment

Radicalization rarely announces itself. It arrives incrementally - through a recommended video, a closed forum, a community that offers belonging alongside increasingly extreme ideas. The internet did not invent political radicalization, but it industrialized it, creating algorithmic pathways that guide vulnerable individuals from mainstream grievance into fringe ideology with a speed and efficiency no previous recruitment infrastructure could match. This book traces the documented history of online radicalization from the early message boards of the 1990s through the social media ecosystems of the twenty-first century, examining how platform architecture, recommendation algorithms, and decentralized network structures created the conditions for extremist recruitment at scale.
Drawing on deradicalization case studies, platform transparency reports, congressional testimony, and investigative journalism, it reconstructs the specific mechanisms through which fringe networks identified, targeted, and retained members across ideological spectrums - from jihadist recruitment pipelines to far-right accelerationist communities. The focus throughout remains systemic rather than sensational.
This is not a catalogue of extreme content but an analysis of the institutional and technological choices - made by platform engineers, regulators, and policymakers - that allowed recruitment infrastructure to develop largely unchallenged for decades. It examines what intervention efforts revealed about the limits of content moderation, the role of community belonging in sustaining radicalization, and the historical precedents that help explain why digital environments proved so effective at accelerating processes that once took years.