Select Page

Unique Organization Identifier (UOI)

RESO UOIRESO’s Unique Organization Identifier (UOI) provides a singular ID for a growing list of individual organizations within the real estate industry. The list includes REALTOR® associations, MLSs, technology vendors, brokers and other affiliated businesses.

For example, from the UOI, you can derive how many MLSs there are in North America.

Data providers should include their UOI in data feeds so data recipients can accurately identify the organizational source (publisher) of each piece of data in an aggregated database.

Technology partners utilizing data should use the UOI to assist with the management of multiple data feeds and overlapping service areas. This helps with clear notation of data originators and allows for easier data deduplication.

Technology partners can also use a UOI to look up association-to-MLS relationships, which can be helpful when an association provides a lockbox or showing service, but the underlying data is from an MLS source that must be linked to the association’s system.

The RESO Data Dictionary includes standardized containers for the UOI (still documented as OUID at this time).


The RESO UOI API (fka RESO OUID API) provides basic information about organizations along with their UOI numbers.

Parameters available for data query include: ouid, active, org, type, city, state, country and zip. This is a public API. No credentials are required to query UOI data. Last updated: 6/18/2024.

Additional formats that are updated daily under the RESO Certification Map can be found on our Certification page. The eventual plan is to replace the service here with what you see there.


Parameter Descriptions


ouid Search by Unique Organization ID (still documented as OUID at this time).
assoc2mls Search by association to an MLS organization.
Example 1:
Example 2:
active Search for active or inactive organizations.
Example of Active:
Example of Inactive:
org Search by an organization’s name or a portion of the name.
Example 1:
Example 2: County

Search by organization type.
Example 1: Association
Example 2: or Provincial Association
Example 3:


Other types include Brokerage, Commercial, Pooled Platform and Technology Company.

city Search by an organization’s city.
state Search by the organization’s state.
country Search by the organization’s country.
Example 1:
Example 2:
zip Search by an organization’s ZIP or postal code.
start-date Returns all records updated on and after the date requested. Date format: YYYY-MM-DD.
end-date Returns all records updated on and before the date requested until the “start-date” or all records prior if the start date is not set. Date format: YYYY-MM-DD.
Example 1:
Example 2:
output To access the UOI data in JSON format.
All parameters can be combined to allow for specific queries:

All listings are available in XML format by plainly requesting:

Note: If accessing the UOI database from a third-party product, the application expects the User Agent header with a valid value.


XML Markup

  <name>Anchorage Board Of REALTORS</name>
   <address>3340 Arctic Blvd, #101</address>

JSON Markup

	"name":"Anchorage Board Of REALTORS",
		 "address":"3340 Arctic Blvd, #101",
"copyright":"2020 RESO. All rights reserved"}

UOI API Update Request Form

Error: Contact form not found.


The RESO UOI is the product of a synergetic effort from industry professionals who offered their time, vision and expertise towards the formation of this project. We are thankful for the contributions of Matt Cohen, Ross Colley, Bill Kellogg, Greg Sax, Rick Sherwood, Clint Skutchan and Allen Wright. 


Subscribe To Our Blog!

Subscribe To Our Blog!

Join our mailing list to receive the latest news and updates from our team.

You have Successfully Subscribed!