This article focuses on the use of Computer-Mediated Communication by the movement for global justice, with special attention to the organisations involved in the movement and its activists. We examined data collected during two supranational protest events: the anti-G8 protest in Genoa in July 2001 and the European Social Forum (ESF) in Florence in November 2002. In both cases, we have complemented an analysis of the Genoa Social Forum and ESF websites with a survey of activists, including questions about their use of the Internet. We then examine hypotheses about changes new technologies introduce in collective action. The Internet empowers social movements in: (a) purely instrumental ways (an additional logistical resource for ‘resource-poor’ actors), (b) a protest function (direct expression of protest); (c) symbolically (as a medium favouring identification processes in collective actors) and (d) cognitively (informing and sensitising public opinion).