MLS IDX Property Data Commingling
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Anticompetitive MLS | IDX Property Data Commingling Rules

Certain MLSs prohibit showing their listings alongside another MLSs listings, producing a poor consumer experience and damaging their Realtor members as a result.  It is time to amend these anticompetitive rules so those in the industry can compete on a level playing field with those that are not.

As an agent or broker, chances are that you don’t know if you’re affected by MLSs who choose to take liberties with how and where your listing data is displayed, especially on your own website.  While I know this is a rather complex and technical subject matter, I encourage you to read on, as it is critical to your business.

Issues Surrounding The MLS Landscape

The ability to display multiple IDX property data feeds on a participant’s IDX website is a widely accepted practice by most MLSs around the country.  Alas, there are still those who hold on to The Old Real Estate principles of “suppress and control” (data), creating a poor user experience for both their members as well as consumers.  This is exacerbated by the continuous splintering and/or consolidation of the greater MLS landscape. Competition is increasing, while politics and money tend to get in the way of logical reason.. suppressing and controlling data creates a poor user experience

Some of the issues that are created by perpetual change across the MLS landscape, especially where information is siloed rather than shared, include:

  • Multiple MLSs populate relatively small Geographic Service Areas (GSAs).  In this case many MLSs overlap in the GSA where a single Realtor might conduct business. As a result, Realtors and brokers must pay to join multiple MLSs and upload their property listings in each for them ensure their entire GSA is covered..
  • A single MLSs GSA may be thousands of square miles in size. In this case a Realtor participant is better served by only showing the subset of listings that are located within their GSA.
  • A Realtor or broker may have a GSA that borders multiple MLSs, except they don’t work the outlying areas of all those MLSs.  In this case the Realtor must be a participant member of multiple MLSs, but only wish to display listings within his or her GSA.

There are many more examples, but you get the point. Providing an accurate, relevant, intuitive property search experience for a broker’s IDX website is a challenge.  Especially when MLSs don’t want to play nice with each other.

If you’re thinking that the number of locations that are served by multiple MLSs is relatively high, you would be right.  The map below shows every zip code in the USA that is served by multiple MLS that BoomTown works with (325+):

Discovery Into The Rules & Regs of MLSs IDX Policy

So, yeah… the problem and the opportunity to improve the user experience and accuracy of property search is a big one.  As such, we set out to provide the most relevant, intuitive, accurate and timely property search experience for consumers on behalf of our MLS member clients and the specific GSAs they work within
A pillar capability to pull this off is that MLSs allow their IDX property data feeds to show results from other IDX property data alongside each other in search result queries. This is often referred to as “commingling”. At the time we understood that there were MLSs out there that did not typically allow for such commingling of data, so we went on a discovery adventure…

During our adventure we reached out to every MLS we work with to get their opinion regarding the commingling of “their” IDX listing data with another MLSs IDX listing data.

Further, we explained that:

  • Our Realtor/broker clients are IDX-participant members in good standing with each MLS that they would like to display listings from.
  • We would uphold each MLS’s display and other requirements.
  • We would not introduce any third-party data (FSBO, etc.) into the search results or property detail records.

We were pleased to discover that many MLSs are just fine with allowing us to display their IDX listings alongside other MLS’s IDX listings in search results, so long as we meet their individual display rules and regulations, and that the member client is also an active participant of each MLS.

Point being, we’re not trying to set a precedent. A precedent is well established.

However, certain MLSs still act as if commingling (co-mingling, the commingles, comangle) is a four-letter word. Answers to our inquiries would come back as simple as a one-word, emphatic, “NO”, while others would go on to explain that the practice was “prohibited” by the National Association of Realtors, only allowed for “certain people”, and even “illegal.”

So, let’s take a look at a response from a MLS that does not like to share. Specifically, their stance is that commingling IDX listing data is prohibited or outright criminal.

“MLSs cannot prohibit participants from downloading and displaying or framing other brokers’ listings obtained from other sources, e.g., other MLSs, non-participating brokers, etc., but can, as a matter of local option, require that listings obtained through IDX be searched separately from listings obtained from other sources, including other MLSs.”

[emphasis mine]

NAR IDX Policy Changes 5/30/12:
Section 18.3  Display-

“Display of listing information pursuant to IDX is subject to the following rules:
Note: All of the following rules are optional but, if adopted, cannot be modified. Select those rules which apply to your IDX program and number the sections accordingly.”

Section 18.3.11

“Listings obtained through IDX must be displayed separately from listings obtained from other sources, including information provided by other MLSs.  Listings obtained from other sources (e.g., from other MLSs, from non-participating brokers, etc.) must display the source from which each such listing was obtained.  Displays of minimal information (e.g. “thumbnails”, text messages, “tweets”, etc., of two hundred (200) characters or less are exempt from this requirement but only when linked directly to a display that includes all required disclosures.”

The Surprising and Unfortunate Perception of MLSs

Turns out that some of the very same IDX property feed police for certain MLSs that believe the practice of commingling is prohibited, illegal, or otherwise have language in their own MLS Rules and Regulations (or related policy documents) that state the opposite and/or would appear to me to be a violation of NAR’s current IDX policies. I’m no attorney but I can read and process simple terms.

I don’t expect anyone to take my word, so let me offer a specific example.

This MLS employee in a position of authority claimed that commingling wasn’t allowed as a matter of NAR IDX policy, (certain names hidden and/or changed, but I assure you the correspondence is verbatim):

From: A.P.  [mailto:xxxxxxxxx]
Sent: Tuesday, May 20, 2014 12:46 PM
To: Xxxx Xxxxxx
Subject: Compliance Question Regarding Co-mingling of Data

Hi Xxxx,

BoomTown is currently building IDX websites for [Clients] that will have co-mingled MLS IDX data, and I’m reaching out to you to clarify whether or not XXMLS permits the co-mingling of your data with other MLSs.  Thank so much for your help, and let me know if I can provide you with any further information.


From: Xxxx Xxxxxxx <>
Date: Tue, May 20, 2014 at 3:49 PM
Subject: RE: Compliance Question Regarding Co-mingling of Data
To: A.P. <xxxxxxx>

We do not permit the co-mingling of XXMLS MLS data with another MLS’ data.  This is true for the NAR IDX policy, so I doubt if many of the MLS’, if any, permit this.

…yet their Rules and Regulations state the contrary:

Sec. 12: An IDX Broker may not modify, enhance or manipulate a Shared Listing. MLS data may be augmented with additional non-listing data not otherwise prohibited IDX Package; Section II IDX Policy, Opt-Out Form, Data Sets Page 4 from display so long as the source of the additional data is clearly identified. In addition, except for listings from other MLS’s, listing information from other sources may not be combined with IDX Listings. For instance, for sale by owner properties and properties not in the MLS may not be combined with the IDX Database.

[emphasis, mine]

In an attempt to pacify their members, some MLSs offer the highly elegant solution (tongue firmly implanted in cheek) of allowing “their” IDX listing data to be displayed on the same website so long as “their” listings are displayed completely apart from another MLS’s IDX listing data.  Because, you know, consumers understand what a MLS is and the GSAs they cover, and it’s completely intuitive to search multiple tabs and pages for property information that covers the same overlapping area.

It bears mentioning that in speaking with a few very educated folks about this specific aspect of the industry, their recommendations all centered around:   “Just do it, everyone else does.”

Alas, we’re not in the business of asking to have complaints filed against us, getting (unjustly) fined, or putting our Realtor and broker clients at risk.

Seriously though… who is subscribing to the ‘just do it’ commingling policy?  Anyone care to share?

The Opportunity For Inter-Industry Cooperation Amongst MLSs

So, MLSs have the option to not allow commingling but the practice is clearly not prohibited by the NAR nor will it get someone thrown in jail. The MLSs that think they’re protecting themselves or their members or the consumer by not allowing commingling of listing data are either sorely mistaken or protecting their own best interests.  In either case, they are putting their very existence at risk by stifling the ability for inter-industry innovation.

The strength of the argument that broker websites powered by the MLS “have the most accurate and complete listing data” compared to the Zillows of the world is fading. More and more brokerages are choosing to not enter property data into an MLS for a multitude of reasons that center around a MLS telling a Realtor/broker what they can or cannot do with *their* (the Realtor/broker’s) property data, while taking liberties with the same.  This “I’ll eat your cake and charge you for it, too” cavalier attitude only serves to diminish the quantitative and qualitative value of MLS/IDX data relative to the portals who are going directly to Realtors and brokers to get *their* listing data.

Further, powerful brokers and brands are moving toward alternative listing distribution networks that allow them to control *their* listing data as they see fit. Cost and complexity are no longer barriers to entry to establishing broker-centric and controlled listing data distribution networks.

How does an MLS fix this issue?  It’s simple.  Go back to your original purpose… maintaining objective governance and compensation reciprocity amongst participating members…  though I would argue that brokers could easily manage the latter.

Since this is highly unlikely to happen in the next few months, how about… change the language in your Terms of Use (or like documentation) to allow for the commingling of broker listing data?

From an actual very large MLS’s Terms of Use:

A Participant or Subscriber may co-mingle listings through IDX from this MLS with listings from other sources on its IDX display, provided all such displays are consistent with these rules. Co-mingling is (a) the ability for a visitor to the site to execute a single search that searches any portion of the IDX database at the same time it searches listing data from any other source(s); or (b) the display on a single web page of any portion of the IDX database and listing data from any other source. Listings obtained from other MLSs must display the source from which each such listing was obtained.  Displays of minimum information (e.g. a one-line or thumbnail search result, text messages, “tweets”, etc. of two hundred (200) characters or less) are exempt from this requirement but only when linked directly to a display that includes all required disclosures.

This very large MLS has the foresight to allow for inter industry innovation rather than suppress it to the direct detriment of every other party except the anticompetitive MLS.

Better question:  How can the NAR fix this issue?  Amend Section 18.3.11:

“Listings obtained through Realtor members, via IDX or other RETS compliant data feed, must be displayed separately from listings obtained from other non IDX sources, (including information provided by other MLSs).  Listings obtained from other sources (e.g., from other MLSs, from non-participating brokers, third parties, etc.) must display the source from which each such listing was obtained.

No programming involved, no shift in day to day business.  Just a couple of simple amendments.

What Can You Do To Help Change These Antiquated MLS / IDX Rules?

We’re going to ask our mutual clients to write each MLS that verbally said no to commingling and officially ask for permission to do so.   If requested, we will point out where their own Rules & Regulations are out of step with the NARs policy and/or explicitly allow for commingling.

A letter very similar in nature to this article was sent to the NAR’s IDX Policy Board for an opinion last week, as some MLSs claim they do not understand how to interpret the NAR’s policy on IDX property feed data commingling.

We are waiting on an answer to provide that extra level of clarity to those who may not see too clearly. After all, we have an MLS employee above who clearly does not know their own policies and are out of compliance with the NAR regarding what language must be used, without modification.

We hope that MLS’ provide their paying members their choice, their right, to be able to compete on a level playing field, to have some reasonable control of *their* data that they pay you to manage.

To expressly deny such directly harms their member participants and the consumer… which creates an air of antitrust.



From the NARs Member Policy Department in reply to an email I submitted requesting guidance on how to properly address MLSs that will not commingle property data from other MLSs and who was responsible for MLSs IDX rules regarding commingling… in it’s entirety:

“I can certainly appreciate Jeff’s opinion.  Ultimately, it’s the local MLS that determines local MLS policy/rules.  And, it’s not as if the decision makers are practitioners, they are.  So, if the question is, how to approach changing local MLS rules to accomplish what Jeff’s believes is in the best interest of brokers, the public and the MLS itself, it’s to have the brokers (MLS Participants) raise the questions locally and debate changing local MLS policy/rules.  Though not everyone will necessarily agree with Jeff’s conclusions.  And I’m not saying that to debate the issue, I’m only pointing out that some would like to maintain control of their local MLS information and not allow it to be comingled with other information.  This is why the option is in the NAR model MLS Rules and Regulations to begin with.”


I’d like to call attention to two sentences:

“Ultimately, it’s the local MLS that determines local MLS policy/rules.”

…ergo, commingling IDX data is not illegal.

“…some would like to maintain control of their local MLS information and not allow it to be comingled with other information.”

…ergo, some MLSs are controlling all of their members property data to their detriment.

There are many IDX companies out there trying to provide a better user experience that are just as prohibited by these rules:



IDX Broker

Diverse Solutions

…just to name a few… are forced to provide ‘workarounds’ which are completely counterintuitive to searching for a consumer looking for property information.

Maybe together we can foster some change in the antiquated world of certain MLSs.

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