THE LANGUAGE OF DATA PART 4 OF 7
The Display Feeds: IDX, VOW, and Publisher
The three feeds that show listings to human beings: your website, your client portal, and your presence on the portals
By Saul Klein and John Reilly September 2026
Every use of MLS data is either display, showing listings to people, or the creation of something new from the data. This article, which stands alone, covers the display side: the three feeds that put listings in front of human eyes, what each one does for your business, and the one rule to remember about each.
IDX (Internet Data Exchange): the feed behind your website. IDX is the program under which every broker in the MLS gives every other broker blanket permission to advertise their active listings on the other broker’s public website, app, and voice devices. It is why a buyer on your site can search every listing in the market, not just yours, and why your listings appear on your competitors’ sites. The visitor is anonymous: no login, no relationship, no obligations. Because it is public advertising, the data is the minimum set, refreshed at least every twelve hours, always with attribution identifying the listing firm and agent and a disclaimer. IDX runs on reciprocity: your listings go into the pool so you can display everyone else’s, and a broker who pulls out loses the right to display other brokers’ listings. The IDX license permits one thing: display, so consumers can identify properties, for personal, non commercial use.
VOW (Virtual Office Website): the feed behind your client portal. Where IDX is your storefront window, a VOW is your desk moved online: a password protected site where a consumer registers, accepts terms of use, and becomes your customer before searching. Because a real broker and consumer relationship exists, the registered client may see substantially more than an anonymous visitor, including sold prices and days on market, the same richer picture the client would get sitting across the desk from you. If your brokerage runs a client portal where buyers log in and see sold data, you are operating under VOW rules whether or not anyone at your office uses the term. Two things are worth knowing. First, the deeper data comes with paperwork: registration records, terms of use, and security obligations sit on the brokerage. Second, VOW exists because the federal government put it there: a 2008 antitrust settlement guaranteed every broker the right to serve clients online with the full data and barred brokers from blocking their listings from a competitor’s VOW. Only a seller can withhold a listing from Internet display, and only for their own property.
Publisher feeds (syndication): the feed behind your portal presence. These run in the opposite direction. IDX and VOW bring the market’s data into your business; publisher feeds send your listings out, from the MLS to the portals and media sites where consumers search. The receiving companies are called publishers because that is what they do: publish listings to the public, under a publisher license that spells out attribution, permitted display, and what they may not do with the data. When your seller asks how the house gets on the big sites, the answer is a publisher feed, and whether it goes out at all is the seller’s call. The listing input asks one question: publish to Internet, yes or no. Yes, and the listing rides every outbound display channel. No, meaning the seller has signed the opt out form, and it rides none of them, while remaining fully visible to every cooperating broker inside the MLS. There is no picking among Internet channels; the election is all or none, full listing or address only, changeable in either direction during the listing.
Three feeds, one shared trait: the license behind each permits display and only display. The listing is shown substantially as it arrived, with rules about attribution, accuracy, and currency. The moment anyone makes something new out of the data, a value estimate, a market report, an analytics product, they have left the display feeds entirely and entered different territory, with different feeds and much stricter licenses. That territory is covered in the companion articles of this series.
This article stands on its own and is also part of the practitioner series “The Language of Data”. Copyright 2026 Saul Klein and John Reilly. All rights reserved. Commentary and general information, not legal advice.
