With the accelerated global warming and the continuous rise of sea level, drastically reducing carbon emissions has gradually become a necessary action for major industrialized countries. Based on the panel data of Chinese cities from 2011 to 2022, this paper empirically examines the heterogeneous impact, mechanism and spatial externality of the development of digital inclusive finance on carbon emissions from the perspective of digital finance by applying the panel double fixed effects model. The study shows that: (1) China's digital inclusive finance index has shown a significant upward trend since 2011, and although there are obvious differences among regions, the regional differences are shrinking. As of 2022, the average carbon emissions per 10000 yuan of GDP in each province are 0.326 tons, with 11 provinces having carbon emissions exceeding this standard, mainly distributed in the underdeveloped central and western regions. (2) The development of digital inclusive finance can significantly reduce carbon emissions, and every 1% increase in the digital inclusive finance index will prompt a 0.311% decrease in carbon emissions. There is some regional heterogeneity in this effect, and for the backward central and western regions, carbon emissions can be reduced by 0.342% and 0.457%. (3) Optimizing regional industrial structure and promoting green technological innovation are important transmission mechanisms for digital inclusive finance to reduce regional carbon emissions. (4) There are also significant spatial positive externalities of digital inclusive finance, which can not only reduce local carbon emissions, but also effectively reduce the carbon emissions of neighboring regions. Finally, corresponding countermeasures are proposed based on the findings of the study.