Social media platforms and practices are now tightly woven into the fabric of everyday politics. This chapter focuses on the role of social media as both a space and a tool for political and civic protest. It conceptualises social media as a constellation of networked publics and argues that these networked publics circumscribe a number of affordances and limitations for protest actors. These affordances can enable or limit specific forms of protest organising and mobilisation, claims-making and information-sharing during the protests. They can also shape the consequences of the attention garnered by protesters’ activities, and the overall risks and tensions encountered by protesters in their interactions with the state and law enforcement. By critically examining these affordances and limitations in the context of the hybrid media system, the chapter argues that the structure of protest opportunities is shaped in equal measure by the technologies of social media platforms; the protest actors, including individuals, institutions, and governments; and the political, spatial and social contexts in which socially mediated protests occur. This analytical complexity is illustrated by case studies of recent protests in Russia, Ukraine and Belarus, which demonstrate how protest affordances of social media can be contentious.