MLS listing is a database that allows a real estate broker representing a seller to widely share the information about the property for sale with real estate brokers representing buyers. It enables a real estate broker to list all the property he wants to sell to the potential buyers. The real estate broker can also retrieve all the information about the properties for sale in a particular area, whether listed by his own brokerage or others.

The MLS acts as an exchange for the real estate agents. But the realtors need to take membership to the MLS in order to put information or to collect information about the other real estate agents. Membership to MLS exchange is only for those people who are part of a trade union. A properly licensed broker, who chooses to neither join the trade association nor operate a business within the associations rules, cannot join the MLS. Similarly, a person who is selling his/her own property cannot put up a listing directly into the MLS.

The realtors in United States can join the National Association of Realtors (NAR), in order to list their property on the MLS. But the NAR restricts the limit of information shown on the MLS by the real estate agents. The Department of Justice (DOJ) has filed an antitrust lawsuit, claiming that NARs policy restricts brokers from establishing websites that show home sellers information that is in the MLS. The DOJ's antitrust claims also include NAR rules that exclude certain kinds of brokers from membership in MLSs. The real estate brokers in Canada can put their listing by membership to the Canadian Real Estate Association (CREA).

There are alternatives available for MLS listing There are websites which allow the licensed realtors or non-realtors to put up their property for sale as well as allow the prospective buyers to search for House/property, without any cost.