MLS API Access Explained for Agents and Brokers

An MLS API is the connection that lets software pull listing data from your multiple listing service automatically, instead of someone typing it in. Today almost every MLS delivers that data through the RESO Web API, the industry standard. To get access, a broker (or a technology vendor working for one) signs the MLS's data license and is approved for a specific use, such as IDX search on a website, a VOW, or a back office tool. The MLS's rules then govern what you can display and how. This guide explains the pieces in plain words, who can get credentials, and what you can build once you have them.

Your MLS data can do more than fill a search box.

How Listing Data Gets From the MLS to Your Site or App

Here is the path, from the listing agent's entry to the screen a buyer sees:

1. The listing agent enters the listing in the MLS.
2. The MLS stores it in a standard format.
3. A data distribution platform (run by the MLS or a company it works with) makes the data available through an MLS API.
4. Your approved vendor or developer connects with credentials tied to your license and use.
5. Your website, app or internal tool shows the data, following the MLS's display rules.

Listing agent → MLS → Data platform (RESO Web API) → Your vendor or developer → Your site, app or tool

You rarely connect to the MLS directly yourself. Your IDX provider or developer does, under an agreement you or your broker sign.

What the RESO Web API Is

RESO, the Real Estate Standards Organization, sets the technical standards MLSs use to share data. Its Web API is the current standard way to move real estate data between systems. It uses common web technology, which means any developer who has worked with modern APIs can work with it.

Two related standards matter:

• The RESO Data Dictionary defines field names and values, so "bedrooms" means the same thing in every MLS that follows it. That makes software easier to move from one market to another.
• RESO certification checks that an MLS or vendor follows the standards. RESO publishes which organizations are certified.

RESO Web API vs RETS

RETS was the older way MLSs shared data, built on bulk downloads. RESO now calls RETS deprecated and no longer supports it, and RESO stopped certifying RETS in 2018. If a vendor still talks about RETS feeds, ask about their plan for the Web API.

	RETS	RESO Web API
Status	Deprecated by RESO	Current standard
How it works	Older format, bulk downloads	Modern web API, request what you need
Developer familiarity	Specialist knowledge	Common web skills

IDX vs VOW: Two Kinds of Access

Most MLSs follow NAR's model policies, set out in NAR's Handbook on Multiple Listing Policy (2024 edition). Two of them decide what kind of access you can get for a consumer-facing site. Your own MLS's rules are what actually apply, so read them.

IDX (Internet Data Exchange)

IDX lets brokers display each other's listings on their own websites and apps, with no sign-up required from the visitor. Under NAR's model policy:

• The brokerage, as the MLS participant, requests the feed, and the MLS must act on the request within five business days.
• The site must be under the brokerage's control and show the brokerage name.
• Each listing must show the listing firm and a way to contact the listing agent or broker.
• Data must be refreshed at least every 12 hours.
• Listings of sellers who asked their broker to keep them off the internet are excluded.
• Other brokers' listings cannot be changed.

VOW (Virtual Office Website)

A VOW is a brokerage website, or part of one, where a consumer who already has a brokerage relationship with you can search MLS data after registering. Under NAR's model policy, the visitor registers with a name and a verified email, and agrees to terms of use. VOW data must be refreshed at least every three days.

	IDX	VOW
Who can see listings	Any visitor	Registered consumers with a brokerage relationship
Registration	Not required by policy	Required
Typical use	Public home search on an agent or brokerage site	Logged-in client portals

Which data each type includes, such as sold data, depends on your MLS's rules and what is public in your state. Ask your MLS.

Who Can Get MLS API Credentials

Access starts with the brokerage. In practice:

• Brokers (MLS participants) can request feeds for their own websites and tools.
• Agents get access through their broker, usually by choosing an IDX provider their MLS has approved.
• Technology vendors and developers sign the MLS's data license and are approved for each specific use, working on behalf of a broker or agent.

The details vary by MLS. As one example, California Regional MLS's IDX resources page describes two routes as of November 2026: use an approved IDX vendor, or request a direct feed by signing a data license agreement, setting up access through its data platform, and describing how the data will be used.

Where MLS Data APIs Come From

Many MLSs distribute data through a platform rather than running the API themselves. Common ones, described from their own sites:

• Trestle from Cotality: a data distribution platform where MLSs approve connections by use case and contract, offering a RESO Web API.
• Spark from FBS: offers the Spark API and a RESO Web API, with a marketplace for data plans, licensing and approvals.
• MLS Grid: MLSs license data to it and approve which vendors can use it; vendors sign one standard license, and the MLS audits compliance.
• Zillow Group's MLS data APIs: a developer platform that offers MLS listing data APIs.

Your MLS decides which platform you use. You do not get to choose.

What You Can Build With an MLS API

Once you have approved access, listing data can power far more than a search box:

• Home search on your own site, with listing pages Google can read
• Neighborhood pages that show current listings and recent activity in each area
• Market reports for your farm area, where your MLS's rules allow
• Saved searches and alerts that keep buyers coming back to your site instead of a portal
• Client portals where logged-in clients search and save homes (a VOW use)
• Agent and broker tools: your office's listings and production, inventory reports, listing presentation prep
• Apps for clients or for your own agents

Each use needs to fit the license you signed. If you want to do something new with the data, ask your MLS first.

Questions to Ask Before You Start

1. Which data platform does my MLS use, and does it offer the RESO Web API?
2. What uses does my license allow: IDX, VOW, back office, or all three?
3. What are the display rules, refresh requirements and disclaimers?
4. What does the MLS charge, and what does the platform or vendor charge?
5. How long does approval usually take?
6. Who signs: me, my broker, or my developer?

When to Build on Your MLS Data

If you want IDX search on a website, an IDX provider is usually the fastest path. Building directly on an MLS API makes sense when you want something an IDX product does not do: a client portal, a custom search experience, market reports in your own design, or internal tools for a brokerage. That is custom software, and it needs a developer who knows both the RESO standards and your MLS's rules.

We build real estate software on MLS data for agents, teams and brokerages. We do not have a published real estate application case study yet, so we will not show an invented one. You can see how your current website and lead capture stand with the free Agent Website Score.

Plan What Your MLS Data Could Do

If you want your MLS data to power more than a search box, book a strategy call. We will look at your MLS's rules, the access you already have, and what it would take to build.