Against the backdrop of advancing the digital economy strategy and improving the market-based allocation of data factors, public data openness has become an important instrument for unlocking data value, promoting digital industrial upgrading, and reshaping the industrial innovation ecosystem. Using Chinese listed firms from 2007 to 2023 as the sample, this paper examines the impact of public data openness on firms’ breakthroughs in key digital technologies. Based on national business registration data, this paper constructs a digital industry linkage index to identify the underlying mechanism. The results show that public data openness significantly improves both the quantity and quality of firms’ key digital technology innovation, and the conclusion remains valid after a series of robustness tests. Mechanism tests indicate that public data openness promotes firms’ key technological innovation through the “forward linkage effect” of upstream digital industries, the “lateral effect” of same-industry digital industries, and the “backward linkage effect” of downstream digital industries, operating respectively through vertical transmission of production factors, competition-induced innovation incentives, and expansion of downstream procurement demand. The effect is more pronounced among state-owned, large-scale, younger, geographically distant from government, and highly digitalized firms, as well as in cities with higher-quality data openness and in high-tech, technology and capital-intensive industries. This paper provides empirical evidence for improving public data openness policies and empowering digital economic innovation and coordinated industrial upgrading.