Listings
What is idx (internet data exchange)?
IDX is the set of rules and feeds that let a brokerage display other members' MLS listings on its own website, so a visitor can search the whole market from one agent's site rather than only that agent's inventory.
IDX is what makes an individual agent's website useful to a buyer. Without it, the site could only show that agent's own listings — a tiny fraction of the market, and rarely what a searcher wants.
Participation is reciprocal and governed by the local MLS: displaying others' listings requires consenting to yours being displayed, and rules cover attribution, refresh frequency, and what may be shown or withheld.
For search purposes, IDX pages are notoriously difficult. They generate large numbers of near-identical, short-lived pages that compete with each other, and the underlying content is not unique to the site showing it.
Related terms
A Multiple Listing Service is a regional database where member brokers publish their listings and agree in advance to compensate other members who bring a buyer, making cooperation between competing brokerages practical.
Syndication is the automatic distribution of a listing from its source — usually the MLS — out to consumer property portals and partner websites, so one entry appears across many destinations.
Real estate SEO is the practice of making an agent or brokerage website rank in search results for the queries local buyers and sellers actually use, and increasingly of being cited in AI-generated answers.
A listing agreement is the contract between a seller and a brokerage that authorises the brokerage to market the property, setting the price, duration, compensation and the extent of exclusivity.