What Is an MLS? How Multiple Listing Services Work
A multiple listing service (MLS) is a cooperative of real estate brokers that pools listing information under a shared set of rules. It is the plumbing behind most U.S. home sales — and the subject of some of the industry's biggest legal and policy fights.
The short definition
The Real Estate Standards Organization (RESO) describes an MLS as an organization that is a collective of brokers and that sets rules for cooperating in sharing and selling listings. Brokers who join agree to follow those rules when working on other brokers' listings, and the other brokers agree to do the same in return.[1]
Participants and subscribers
In MLS terms, member brokers are participants and their agents are subscribers. Agents generally join under a participating broker rather than on their own.[1]
Who owns an MLS?
According to RESO, most MLSs are owned by the REALTOR® association that formed them, some are owned jointly by several associations as a regional MLS, and some were formed and are owned directly by groups of brokers. Some association-owned MLSs are run by association staff; others are separate organizations with their own staff.[1]
For REALTOR®-owned MLSs, national policies set by the National Association of REALTORS® (NAR) apply alongside each MLS's local rules. NAR publishes them in its Handbook on Multiple Listing Policy, which contains both mandatory and recommended rules.[1][2]
How many MLSs are there?
RESO says it tracked 484 MLS systems in the United States as of August 2026.[1] Consulting firm T3 Sixty likewise counted 484 U.S. MLSs as of December 31, 2025, down from 514 a year earlier and from roughly 850 in 2015, alongside 991 local REALTOR® associations.[3] The decline reflects years of MLS mergers and data-share agreements — see our Mergers & Consolidation coverage and our guide to the largest MLSs in the U.S.
What an MLS does
- Listing database. Participants enter their listings in a standard format so every other participant can see and show them.
- Rules and compliance. MLSs set and enforce rules on data accuracy, listing submission and status changes, and can fine members who break them.
- Data distribution. MLS data powers brokers' own websites through IDX (Internet Data Exchange) feeds and is syndicated to portals under license. RESO maintains the data standards — the Data Dictionary and Web API — that let these systems talk to each other. See RESO & data standards.
Why MLS rules are in the news
NAR's Clear Cooperation Policy requires listings that are publicly marketed to be submitted to the MLS within one business day.[4] Some brokerages argue rules like this limit sellers' choices; many MLSs argue they keep the market fair and transparent. That disagreement is at the heart of the Compass–MLS lawsuits. Separately, the 2024 NAR settlement removed offers of buyer-broker compensation from MLSs.
Sources
- RESO — MLS FAQ — Real Estate Standards Organization
- Handbook on Multiple Listing Policy — National Association of REALTORS®
- 2026 Real Estate Almanac indices (MLS and association counts) — T3 Sixty
- MLS Clear Cooperation Policy — National Association of REALTORS®
This guide is original MLS Daily News reporting based on the sources above. It is general information, not legal advice. Found an error? See our corrections policy.
