Real Estate Glossary > M > Multiple Listing Service (MLS) Definition

The MLS is a local or regional service that compiles available real estate for sale by member brokers along with detailed information brokers and agents can access online. Redfin is a MLS-powered website, which means we can show you all the homes for sale, faster than any other site since we sync directly with the MLS in every market we serve. Local MLS organizations have their own rules and systems for providing listing information. Over half of the MLSs in the United States are affiliated with the National Association of Realtors (NAR); in other cases, MLSs operate as private businesses but with oversight from major local brokers. Some MLSs publish their own websites for consumers to access listing data directly from the MLS, but mostly MLSs share data by offering a data feed for member brokerages to build their own websites. The most common feed for an MLS to share data with a brokerage website is an Internet Data Exchange (IDX) feed, designed to publish a limited set of information that all consumers can see without registration.

Many MLSs also offer a Virtual Office Website (VOW) feed, which publishes data intended only for brokerage clients. Because of a 2008 Department of Justice settlement with the National Association of Realtors, MLSs owned by the National Association of Realtors must offer a VOW feed, and that VOW feed must include all the MLS data that a broker could share with a client face to face. Due to MLS rules, consumers wishing to access VOW data on a brokerage website must first register on that website, agree to MLS Terms, and validate their email address. Agreement to MLS Terms doesn't obligate you to buy or sell a home with a Redfin agent. Redfin offers VOW data in every market we serve where that data is available. Media websites that host advertisements from real estate agents are not generally allowed to use MLS data, and instead get data by negotiating with individual brokerages for a data feed. A 2008 third-party study estimates that these websites only publish 70% of the homes for sales in any given market.