Extreme digital speech (EDS) is an emerging challenge that requires co-ordination between governments, civil society and the private sector. In this report, a range of experts on countering extremism consider the challenges that EDS presents to these stakeholders, the impact that EDS has and the responses taken by these actors to counter it. By focusing on EDS, consideration of the topic is limited to the forms of extreme speech that take place online, often on social media platforms and multimedia messaging applications such as WhatsApp and Telegram. Furthermore, by focusing on EDS rather than explicitly violent forms of extreme speech online, the report departs from a focus on violence and incorporates a broader range of issues such as hateful and dehumanising speech and the complex cultures and politics that have formed around EDS.