This paper manually matches carbon emission data from administrative boundary areas of 285 Chinese cities from 2006 to 2020 and investigates the impact of public data openness on carbon emissions in these areas, along with the underlying mechanisms. The findings reveal that public data openness significantly addresses the carbon emission challenges in boundary areas, with high-quality data openness further enhancing this effect. The mechanism analysis indicates that the reduction in information costs and the suppression of government-business collusion are the primary channels through which this effect operates. Public data openness in border areas has facilitated green technological innovation and improvements in energy efficiency. However, this effect is mainly observed in cities with advanced information technology. Its impact on the urban industrial structure is reflected in the digitalization of industries rather than the industrialization of digital sectors. Insufficient information infrastructure and contiguous poverty-stricken areas weaken the carbon reduction effect of public data openness in border regions. The conclusions of this study provide theoretical insights for spontaneous low-carbon development in administrative boundary areas in China during the data-driven era.