Given the continued rise of transnational and domestic terrorism, countering the appeal of extremist ideologies and organizations is increasingly becoming a top policy priority for governments around the world. Crucial to challenging extremist ideology and violence is the role of civil society organizations that are operating in this highly contested ideational and social space. After years of unfruitful government-led strategic communications campaigns, policymakers are now focusing on empowering credible voices at the grassroots level to expand their communications reach among individuals and communities vulnerable to the appeal of violent extremism. Yet, while U.S. and European governments shif towards prioritizing a surrogate strategy for combatting extremist propaganda, there is very little understanding of the eficacy of counter-ideological civil society initiatives already operating in this space. As concerns about violent extremism grow, there is a troubling knowledge gap between those operating at the grassroots, community level and in government and law enforcement agencies. This report aims to fill that gap by highlighting best practices and identifying areas of vulnerability in CSO and private sector campaigns against extremism.