Described are computing systems and methods, computer program products, and application programming interfaces (APIs) or web requests that facilitate code sharing between operators of e-commerce platforms. In accordance with various embodiments, a codeshare principal shares its inventory and other functionality with a codeshare partner to thereby expand its customer base. Requests from the partner to the principal include identifiers of the partner as well as the partner's user, allowing the principal to track its extended customer base and tailor restricted offers to users of affiliated partner systems.