The internet can leave users vulnerable to social challenges, which creates opportunities for extremism to spread. Users can be exposed to extremism in multiple ways, including through recruitment and socialisation. Extremist content may be found on mainstream social media sites and ‘alt-tech’ platforms, which replicate the functions of mainstream social media but have been created or co-opted for the unconventional needs of specific users. Automatic detection can be used to moderate extremist content on a large scale. However, this is prone to false positives and may disproportionately impact a particular group, which can fuel mistrust in the state. Many stakeholders believe that current counter-extremism responses are too focused on law and technology, and do not address the underlying reasons that people are drawn to extremist content. Individual and societal interventions aim to identify underlying socio-economic and cultural contributors and implement protective factors to reduce how many people develop extremist views.