We study how broadband penetration affected social capital in the UK. Our empirical strategy exploits a technological feature of the telecommunication infrastructure that generated variation in the quality of Internet access across households. Merging information on the topology of the broadband network with geo-coded longitudinal data about individual social capital, taken from the British Household Panel Survey, we show that access to broadband Internet caused a significant decline in civic and political engagement. Overall, our results suggest that the introduction of fast Internet crowded out several aspects of social capital.