Digital technologies provide important support for firms to break through technological path dependence and deepen their embeddedness in innovation ecosystems, which is of great significance for expanding corporate technology niches and building sustainable competitive advantages. Drawing on the digital technology affordance theory, this paper uses data from A-share listed companies in Shanghai and Shenzhen from 2010 to 2023 to empirically examine the mechanisms and boundary conditions through which digital technology application affects corporate technology niche expansion. The results show that: (1) Digital technology application promotes corporate technology niche expansion, because digital technology affordance provides an action basis for firms to cross technological boundaries and extend into multiple technological fields. (2) The resource integration effect generated by functional affordance and the actor collaboration effect generated by relational affordance are the key mechanisms through which digital technology application facilitates corporate technology niche expansion, and these two mechanisms further form a chain mediating effect. (3) External market and institutional environments exhibit differentiated moderating effects. Specifically, market dynamism strengthens the positive effect of digital technology application on corporate technology niche expansion, whereas intellectual property protection intensity weakens this effect. This paper not only expands the applicability of the digital technology affordance theory in the study of the evolution of corporate technology niches, but also provides theoretical support and practical implications for firms to formulate digitally-oriented strategies for technology niche expansion in complex environments.