Assess the structural role of social media platform design in facilitating Salafi-jihadist radicalization and recruitment over the decade 2015-2025, and evaluate the comparative effectiveness of platform-level, state-level, and community-level counter-extremism interventions.

Systematic review of peer-reviewed and grey literature 2015-2025 on online radicalization pathways; analysis of platform transparency reports and EU TCO compliance data; comparative case analysis of counter-extremism program evaluations across Europe, North America, and Southeast Asia; synthesis of ICSR, VOX-Pol, and GNET datasets on foreign terrorist fighter flows and online recruitment patterns.

ISIS at peak produced an estimated 38,000-90,000 social media accounts across Twitter and Facebook, generating approximately 90,000 tweets per day before coordinated takedowns. Post-deplatforming studies found that 95% of suspended ISIS-affiliated Twitter accounts migrated to Telegram within 30 days.

EU Terrorist Content Regulation mandated 1-hour takedown windows; compliance rates reached 96% among major platforms by 2024, but researchers documented a 340% increase in Telegram-hosted content in the same period, indicating displacement rather than suppression.

The EU Internet Forum cross-platform referral mechanism processed 65,000+ referrals 2015-2024 with a 94% removal rate; however, randomized evaluations of counter-narrative video campaigns found effect sizes near zero on attitude change among pre-radicalized individuals.

Community-based CVE programs in Denmark under the Aarhus Model achieved 84% disengagement rates among active participants. Foreign terrorist fighter flows to Syria and Iraq peaked at 40,000 individuals from 110 countries in 2013-2016, with online recruitment identified as a contributing factor in 73% of Western cases analyzed by ICSR.