RESO Web API Definition

RESO Web API is a data technology standard for the real estate industry designed to streamline the movement of listings data across MLS, reduce local hosting and security costs for agents and brokers, and push real estate product development deeper into mobile and social applications.

Still not clear? Don’t worry. We’ll break this definition down piece by piece.


We begin by saying RESO Web API is a data technology standard. A data technology standard essentially sets the rules of the game.

In real estate there are probably thousands of MLSs and developers working on real estate technology products, websites, and applications every day.

Each of these requires a data transfer (usually property listings) from one source to another. As a data technology standard, RESO Web API provides the technical guidelines for how this should be done.

This allows everyone to be on the same page, which saves time and money.


In the next part of the definition we say that RESO Web API is designed to streamline the movement of listings data across MLS.

The fact of the matter is that the real estate industry is decentralized. There is no central organization warehousing listings across the United States. Instead, there are 500+ small to medium MLSs.

Without standardization, each MLS might use its own framework. That would present a nightmare for agents wanting IDX or developers looking to launch real estate products.


Next we say that RESO Web API should help reduce local hosting and security costs for agents and brokers.

This has to with an older real estate technology standard known as RETS.

RETS was the RESO Web API of the early 2000’s.

It provided the principal framework for real estate data transfers from 1999 to 2018, when the Real Estate Standards Organization (RESO) announced it would replace RETS with RESO Web API.


But RETS came with a few trade offs. Because it requires duplication of the MLS database on local servers, it increases hosting and security costs for agents wanting IDX.

RESO Web API, on the other hand, helps limit these costs by allowing IDX software to call directly from the MLS.

For a full explanation of how RESO Web API works, check out What is RESO Web API,


The last part of our definition concerns mobile and social applications. RESO Web API is based on OData, a global technology protocol.

OData is a set of best practices for working with APIs. It’s a popular framework with a large developer community.

Giving developers a familiar foundation should help speed the developmen of their products and push the real estate industry into more cutting edge technologies.

So there you have a definition for RESO Web API. Did we miss something? Leave it in the comments. For more real estate definitions, check out Real Estate Listing Data Explained.

Rate our blogs


The opinions or information expressed in this article are those of the author and do not necessarily reflect the official views, policy, or position of Realtyna. The information on Realtyna’s Website is general, for informational purposes only, and is not to be relied upon or interpreted as real estate, legal, accounting, or other professional advice or a substitute. Please discuss anything related to the certification process, professional advice or legal procedures with your MLS providers.

Stay Up To Date

Get the Knowledge you need Delivered Straight to your inbox

No Comments

Sorry, the comment form is closed at this time.