BigTech firms increasingly integrate financial services into their platform ecosystems, raising a central question: how this integration affects firms’ core business activity. Using a large-scale field experiment at one of the world’s largest e-commerce platforms (over 2.5 million individual-month observations), we estimate the causal effects of marginal expansions in access to embedded credit. We find that credit access increases user economic activity—raising intensity and persistence, stabilizing demand, and expanding consumption scope—with little evidence of consumption upgrading or increased delinquency. Our results show that embedded credit reinforces the platform’s core operations, highlighting complementarities in modern digital ecosystems.