In the late 1800s, real estate agents gathered at local associations to exchange information about the homes they were trying to sell. The intuitive logic was that the best way to make a sale was to spread the word.
The real estate market has evolved considerably since then, but buyers and sellers, typically through their agents, are still trying to solve the same information problem. Buyers look for homes with specific features, such as location, number of rooms, and lot size, while sellers look for buyers whose preferences match the home they are selling. Real estate agents play a central role in this matching process by building a network that raises the likelihood of a timely sale.
Today, the leading real estate listing database is the Multiple Listing Service (MLS). It traces its origins to San Diego in 1885, when the local real estate board would distribute daily listings to its members. The MLS is not a single entity; it is composed of roughly 500 local real estate organizations, which are owned or controlled by brokers and associations in their respective territories. Members create the listings, while the regional MLSs distribute them to other agents and to public-facing websites such as Zillow, Redfin, and Realtor.com.
There are clear efficiencies from having a single, comprehensive database to economize on search costs and to raise the odds of a timely match. The tradeoff, however, is that, within a given territory, a viable second source of listings is unlikely to emerge. This raises the concern that whoever controls the listings data controls the terms of competition involving those listings.
This is exactly the issue at the heart of the recent antitrust dispute between Zillow, on one side, and Midwest Real Estate Data (MRED), a regional MLS serving the Chicagoland area, and Compass, the nation’s largest real estate brokerage, on the other. Zillow depends on MRED for listings in the Chicagoland area, where, according to Zillow’s complaint, MRED holds a 98% share.
The Rise of Private Listing Networks
Private listing networks (PLNs) have recently gained ground in real estate. Zillow defines them as “listings that are not visible to the general public on consumer-facing real estate websites and are often excluded from MLSs.” Instead, agents market these properties to a closed network of buyers’ agents, often from the same brokerage as the listing agent.
MRED has operated its connectMLS Private Listing Network since 2016. It functions as a separate database where agents place “draft” listings. These properties remain in a kind of pre-listing limbo until agents move them to the general, public MLS database.
Compass launched its own private listing network in 2024. It uses a three “phase” approach for listings. Phase one is called “Compass Private Exclusive,” where a listing is only circulated among Compass’s closed network of agents and clients. Phase two is called “Compass Coming Soon,” where a listing is moved to Compass’s website and to partner websites—but the listing is still not part of the MLS database. For listings that have not sold, there is a phase three, where the listings are moved to the general MLS database and public portals such as Zillow. Notably, reports indicate that 94% of phase one listings reach phase three.
Why Sellers Choose Private Listings
The growth of PLNs raises a key question: If the real estate market is fundamentally about finding matches to spur transactions, why would a seller agree to limit exposure of their listing to a closed network when it could immediately enjoy wider visibility on the MLS database? Below, I explore several possible answers.
The first potential explanation is the classic principal-agent problem, where the incentives of the principal and agent do not fully align. In a notable study, “Market Distortions When Agents Are Better Informed,” Steven Levitt and Chad Syverson examined how real estate agents behave when selling their own homes compared with their clients’ homes. When they sold their own homes, the agents were generally more patient (keeping their homes on the market for 9.5 days longer), which resulted in a higher sale price (approximately 3.7% higher).
In contrast, since agents only keep a small percentage of an incremental sale price for a client, but bear the full cost of marketing a home for longer, they have incentivizes to sell client properties too quickly and cheaply. Interestingly, the data used in the study comes from suburban Cook County in Northern Illinois, which is an area that MRED covers.
Given this context, the principal-agent issue for PLNs is that seller agents may prefer to start a listing on a PLN because they save on the costs associated with a widespread, public marketing campaign. Additionally, the use of a closed network is more likely to keep the sale within the same brokerage, a practice called “double-ending.” According to the complaint, sales that are made “off-MLS” double-end 31% of the time versus 18% for regular, “on-MLS” sales. This clearly benefits large brokerages like Compass by keeping more of the commissions in-house.
A second possible explanation is that exclusivity can help promote a home, even among a smaller group of buyers and agents. Specifically, having access to a closed network can create a sense of urgency and encourage buyers to act quickly (akin to a pre-sale reserved for loyalty-card customers at retail outlets).
There is also a question of whether a seller is giving up bargaining leverage inside a PLN—as there is always the option to later move the listing to the public database. Nonetheless, a risk-averse seller may take a bird in hand over a prolonged and uncertain listing period in the open market.
A third explanation is privacy. An exclusive listing may appeal to homeowners who do not want to publicize a sale. A prerelease may also help gather feedback from other agents and refine the listing price. It is unclear, though, whether those benefits require an exclusive period or merely sufficient research before the public listing.
The empirical record on whether sellers benefit from private listings remains unsettled, and studies sponsored by interested parties complicate the picture. Depending on the source, sellers fare either better or worse. Comparisons may not involve genuinely similar properties because the homeowners and agents who choose private listings may differ systematically from those who do not, a problem researchers call selection effects. More rigorous studies using updated data could provide a clearer answer.
How Private Listings Shift Market Power
Whatever motivates the growth of private listing networks, their rise changes the competitive dynamics between real estate platforms such as Zillow and brokerages such as Compass. If most buyers find homes through Zillow, Zillow enjoys greater traffic, more advertising revenue, and greater bargaining power over various affiliate or referral agreements. If, instead, more buyers find homes through agents, then the economic rents shift to brokerages—particularly those such as Compass who control a significant share of local inventory.
Exclusive listings can also help a brokerage attract clients. If sellers and buyers believe Compass has the newest and most desirable listings in a market, particularly when inventory is low, access to that network becomes a reason to hire a Compass agent rather than browse a platform such as Zillow.
Relatedly, if public portals only receive “leftover” homes that did not sell during the private period, then this changes the nature of their databases and creates greater demand for PLNs operated by brokerages like Compass.. In its complaint, Zillow warns that “[l]osing access to listings and having lower-quality listings would risk triggering a harmful feedback loop that would degrade Zillow’s platform further.”
Zillow’s Response to Private Listings
In April 2025, Zillow announced that it would no longer display homes previously marketed through a closed private listing network. Zillow does offer exceptions for homeowners seeking greater privacy through a limited release.
Zillow argues that sellers’ agents remain free to use private listing networks, but they cannot have their cake and eat it too—i.e., by later obtaining public distribution through Zillow. In its view, allowing them to do both would put Zillow at a competitive disadvantage and reduce the quality of its platform as it competes to match buyers with sellers.
Zillow emphasizes that it adopted the policy unilaterally. Generally, antitrust treats unilateral acts fundamentally differently than coordinated ones because the latter can circumvent natural rivalries that benefit consumers.
Of course, under certain conditions, unilateral acts can also impair the competitive process. Those conditions typically involve assessments of market power in a properly constructed relevant market, offsetting procompetitive justifications. It must also account for the Supreme Court’s ruling in Trinko, which emphasized that firms generally have no antitrust duty to deal with competitors. That principle is likely even stronger when competitors seek access while attempting to disadvantage the firm in other areas.
The Fight Moves Beyond the Courtroom
In June 2025, Compass sought a nationwide preliminary injunction—a court order that would have blocked Zillow’s policy while the case proceeded. In February 2026, U.S. District Judge Jeannette Vargas of the Southern District of New York denied the motion because Compass had not shown that its antitrust claims were likely to succeed.
Among her key findings, Vargas concluded that Compass had not shown that Zillow possessed enough market power to exclude competitors. She also found no evidence supporting Compass’ allegation that Zillow had colluded with Redfin to implement the private-listing policy. The court therefore concluded that Compass had failed to establish a likelihood of success on the merits. Compass later voluntarily dismissed the case.
According to Zillow’s complaint, the conflict continued outside the courtroom. In October 2025, Compass’s CEO sent messages to at least eight MLSs urging them to discipline Zillow, and if Zillow did not drop its PLN policy, to block their listing feeds to the platform. A few weeks later, MRED revised its display rules to promote “non-discrimination” that implicated Zillow’s PLN policy. MRED’s CEO informed Zillow that it would cut off the company’s access to the MRED feed if it enforced its policy.
Over the ensuing months, Compass-owned Coldwell Banker brokerages terminated more than direct listing feed agreements with Zillow. Finally, on May 8, 2026, Compass terminated all Compass or Compass-owned brokerage feeds to Zillow nationwide.
Meanwhile MRED and Compass announced a partnership on April 24, 2026. Compass agreed to provide MRED with its national inventory of Private Exclusive and Coming Soon listings, which MRED will make available to its PLN participants. Further, Compass agreed to subsidize MRED membership fees for the first 100,000 Compass agents to join MRED as full members. For its part, MRED committed to protect agents participating in its PLN from being banned or penalized by third-party portals like Zillow.
Zillow’s Antitrust Claims
Zillow alleges that MRED and Compass violated Section 1 of the Sherman Act, pleaded as a per se unlawful group boycott or, at the very least, a violation under the rule of reason. The theory is that MRED and Compass agreed to protect their joint interests and deny Zillow a critical input—that is, MRED’s Chicagoland feed—unless Zillow abandoned its PLN policy. Notably, Zillow argues that the conspiracy began well before the formal April 24, 2026, partnership announcement.
Zillow separately alleges a Section 2 claim against MRED for monopoly maintenance—based on the theory that Zillow is a nascent competitor in the listings database market through its Zillow Preview product. This recent product offers brokers the opportunity to “preview” their listings before moving them to the larger MLS database.
Compass and MRED accuse Zillow of using the Preview product to do the same thing that it claims harms consumers and the market. Zillow responds that it isn’t a private database only available to a select group of agents. Instead, Zillow contends that Preview is a public listing that merely exists outside of the MLS database. Additionally, Zillow highlights that MRED faces little to no competition in real estate listings in the Chicagoland area.
The Core Question: Competition or Exclusion?
The rise of private listings is at the center of this antitrust dispute, and the empirical evidence on whether this results in better outcomes for sellers is still emerging. But ultimately, the case is not about whether private listings are good or bad for market participants.
Moreover, the case is not fundamentally about Zillow’s unilateral PLN policy or even Compass’s response. Rather, the case boils down to the partnership between Compass and MRED, and whether that partnership includes an agreement to jointly withhold listing data from Zillow. Such an agreement, if proven, raises legitimate questions about whether the group boycott impairs the competitive process and is using a vertical supply chain partner (i.e., MRED) to leverage market power to advantage Compass in its horizontal competition in listings discovery with Zillow.
Group boycotts have a long history in antitrust law, as I document in a recent article. The court must now decide whether this was vigorous competition over listing strategies or concerted exclusion from a critical source of data. That question has consequences beyond the courtroom, particularly given the congressional attention that private listing networks have attracted.
