IDX stands for "Internet Data Exchange" and is an umbrella term used to cover policies, standards, and software pertaining to the display of real estate listing information on websites. IDX is what enables members of a multiple listing service (MLS) to integrate real estate listings from the MLS database into their own websites. IDX is not a website itself, but rather software that allows anyone to share the MLS data on a third-party website. IDX is a system that allows real estate agents and brokers in the US to show MLS property listings on their websites. IDX is a fast and virtually effortless way to populate listings, allows agents to display more listings on their websites, and helps an agents listings to gain more exposure.