RETS

RETS stands for Real Estate Transaction Standard, a data-exchange protocol used in the residential real estate industry to transfer property listings and related information between Multiple Listing Services (MLS), brokerages, and consumer portals. It was developed under the auspices of the Real Estate Standards Organization (RESO) and became a widely adopted method for automated data sharing in North American MLS ecosystems beginning in the late 1990s and early 2000s.

Technical overview: RETS operates over HTTP and uses a login-based session model with a sequence of commands such as LOGIN, LOGOUT, SEARCH, and GETOBJECT. Data is described and navigated through metadata, which defines Resources (for example Listings), Classes, and Fields. Clients issue search queries against the server, request metadata, and retrieve data objects in a structured format.

Data formats and metadata: RETS provides a metadata-driven approach to describe the data model. Listings and related records are exposed through defined Resources and Classes, with Fields specifying the data elements. Historically, payloads could be delivered as XML or tabular formats, and GETOBJECT responses could retrieve binary objects such as photos. The metadata enables clients to adapt to varying data schemas across MLSs.

Adoption and evolution: RETS remains in use in many MLS environments, but its role has evolved as RESO and the industry move toward modern RESTful APIs, such as the RESO Web API, to provide similar data access with contemporary web standards. Some MLS organizations continue to maintain RETS endpoints alongside newer interfaces, while others have migrated fully to REST-based solutions. Security typically relies on TLS encryption and authenticated sessions.