Young people – politicised, active and highly connected – are no longer just passive consumers of online terrorist content by adult groomers but are themselves propaganda creators, group organisers, peer recruiters, extremist financers and terrorist convicts. This process, called “youth‑on‑youth radicalisation”, emphasises the agency that young people have in a digital era in which the information hierarchy is increasingly flattened. Noting the formation of several new young extreme‑right groups and a series of terrorist convictions across Western Europe, this paper takes first steps to investigate the specific nature of this emerging threat.