The increasing integration of modern information technologies into policies promoting market efficiency raises persistent concerns about the technological transition costs they impose on market participants. This study provides novel direct evidence of the existence of such costs and causally identifies their consequences for price discovery. Our unique empirical setting is the Securities and Exchange Commission's 2016 adoption of a more secure data communication protocol for its online repository of corporate disclosures. During the first year of implementation, some users failed to adapt to the new protocol, which prevented them from accessing electronic filings and disrupted the processing of company disclosures. We show that these technological frictions reduced price informativeness for firms publishing new reports, consistent with the idea that higher information acquisition costs diverted resources necessary for interpreting the filings. Supporting this mechanism, we demonstrate that transition costs also undermined informed trading activity. We further explore heterogeneity and find that the negative impact of technological barriers is less pronounced when users were more sophisticated, when firms concurrently announced earnings, and when reports were less complex. Our results highlight that technological transition frictions are a first-order concern for policymakers and underscore the critical need to manage them within regulatory frameworks.