Internet Data Exchange, or IDX, refers to the policies and technology that allow real estate brokers to display each other's MLS listings on their own websites. It is what makes it possible for an individual agent's site to show a broad range of homes for sale, not just their own listings.
Under IDX rules, participating brokers consent to have their listings shown on other members' sites, subject to standards about attribution and display. The listing data is typically fed automatically from the MLS.
IDX benefits consumers by making listings widely accessible and benefits agents by keeping visitors on their own websites. It differs from a VOW in that IDX generally shows publicly available information without requiring visitors to register or log in.