MLS

An MLS (Multiple Listing Service) is a database maintained cooperatively by real estate brokers that aggregates property listings from all member agents in a region. In the US, the MLS is the authoritative source for active, pending, and recently sold residential listings.

MLS data is arguably the most comprehensive real estate database in a given market because listing agents are required to submit listings to the MLS as a condition of broker membership. This makes MLS data significantly more complete than any individual portal.

Historically, MLS data was accessible only to licensed brokers. Today, platforms like Zillow and Realtor.com aggregate and display MLS data publicly, and APIs built on top of these platforms make MLS-sourced data accessible to developers building real estate applications.