The rapid development of the Internet has significantly impacted various socio-economic activities. Using Chinese Industrial Enterprise database and Industrial Enterprise Pollution database, this research examines the impact and mechanisms of Internet development on CO2 emissions. The key findings are as follows: (1) Internet development has substantially reduced the CO2 intensity of enterprises, and this conclusion remains robust even after performing a series of robustness analyses. (2) The major mechanisms responsible for the reduction in CO2 emissions are productivity improvement, technological innovation, and energy structure adjustment. (3) The analysis of heterogeneity reveals that the effect of Internet development on CO2 reduction is more pronounced in coastal areas, areas with a high share of secondary industry, low-carbon industries, clean industries, small-scale enterprises, and export enterprises. This study provides empirical evidence supporting China’s “Internet+” strategy and its progress towards achieving the “Carbon Peaking and Carbon Neutrality Goals.”