Abstract: The impact of internet development on carbon productivity is closely related to the industrialisation stage. Based on panel data from 154 economies from 1996 to 2019, this study systematically examines the impact of internet development on carbon productivity from the perspective of industrialisation stage evolution. This study found that: (1) Internet development has a significant positive effect on carbon productivity improvement; (2) When industrialisation level is used as a threshold variable, there is a double threshold effect of internet development on carbon productivity, especially as industrialisation enters the later stage, the positive effect becomes stronger; (3) Mechanism testing shows that internet development inhibits technological progress in the early stage of industrialisation, improves resource allocation efficiency in the middle stage of industrialisation, and promotes technological progress in the later stage of industrialisation to affect carbon productivity; (4) China is currently in the middle stage of industrialisation and should continue to promote internet development, improve industrialisation level, and stimulate the potential of resource allocation efficiency in improving carbon productivity. Therefore, policymakers in each economy should accelerate internet development, promote the synergy between industrialisation and internet development, and focus on practical policy efforts.