How MLS Listings Propagate: RETS, IDX, and Real Estate Portals

When your home is listed in the MLS, it doesn’t just appear in one place. That single MLS entry becomes the source data that feeds hundreds of other real estate websites. Understanding how this system works helps sellers set realistic expectations about timing, accuracy, and why changes don’t appear everywhere instantly.

The MLS Is the Source of Truth

The Multiple Listing Service (MLS) is the original data source. It is where the listing is created, maintained, and officially updated by the listing brokerage.

Once a listing is active in the MLS:

The MLS becomes the authoritative record for price, status, photos, and property details
Other websites do not create their own versions of the listing
They receive data from the MLS through technical data feeds

This is why accuracy at the MLS level matters more than anything else.

What a RETS Server Is

Real Estate Transaction Server or RETS are used to share information from the MLS A RETS server (Real Estate Transaction Standard) is a data system used by MLS organizations to distribute listing information to approved participants.

In simple terms:

The MLS stores listing data
The RETS server provides a standardized way for other systems to access that data
Authorized websites and brokerages pull listing updates from the RETS server on a schedule

RETS does not push data instantly. Most systems poll the MLS at intervals (for example, every 15 minutes, hourly, or several times per day).

What IDX Is (and What It Is Not)

IDX stands for Internet Data Exchange. IDX is what allows brokerages to display MLS listings on their own websites.

Key points about IDX:

IDX websites pull listing data from the MLS via RETS or similar feeds
IDX sites display listings according to MLS rules and permissions
IDX sites do not control the original data—they display what the MLS provides

Real Estate Two70’s website uses IDX to show active listings. When your listing is entered into the MLS, it appears on our site automatically once the IDX feed refreshes.

What Real Estate Portals Are

Real estate portals are large consumer-facing websites and apps that aggregate listings from many MLS systems. Examples include national home search platforms and regional listing sites.

These portals:

Are created to attract you to their site, get you to sign up, and then sell your information to real estate agents in the form of lead referrals. This practice takes a portion of every commission and reroutes it to a large company. Participating in portals as a consumer eventually sends part of the fees you pay out of the community, rather than to a local agent who will spend his or her commission locally, supporting local businesses.
They Refresh data on their own schedules
They may display listings slightly differently based on their internal systems

Importantly, portals do not update in real time. Each portal decides how often it refreshes MLS data. Some portals can take a few minutes and others can take 24 hours.

How All of This Works Together

Here’s the simplified chain:

The listing is created and activated in the MLS
The MLS makes the data available through its RETS (or similar) server
IDX websites and portals pull the data on their scheduled refresh cycles
The listing appears across dozens or hundreds of websites over time

Because each system refreshes independently, listings do not appear everywhere at the same moment.

Why Propagation Takes Time

Sellers often expect instant updates everywhere. In reality, delays are normal and expected.

Some IDX sites refresh multiple times per day
Some portals refresh hourly
Some portals refresh only a few times per day
Photo-heavy updates often take longer to appear

A price change, new photos, or a status update may show immediately in the MLS but take hours—or sometimes a full day—to fully propagate across the internet.

Why Sellers Sometimes See Inconsistencies

Temporary inconsistencies can happen during propagation. Common examples:

A price change appears on one site but not another yet
Photos appear in a different order
A status update lags on a third-party portal

These usually resolve automatically once all systems complete their next refresh cycle.

What Sellers Should Focus On

The most important things sellers can do:

Ensure the MLS listing is accurate before it goes live
Understand that propagation is not instant
Report persistent errors to the listing agent rather than trying to fix portal sites individually

Because the MLS is the source of truth, corrections should always start there.

Questions About Where Your Listing Appears?

If you’re wondering why your listing shows up on some sites before others—or why an update hasn’t appeared yet—we can explain what you’re seeing and confirm that the MLS data is correct.

Contact a Two70 Agent Learn About Creating the MLS Listing

Related Seller Process Pages

Note: This page is part of the Seller Guides & Process series.

FAQ

Why does my listing show on some sites but not others yet?

Each IDX website and portal refreshes MLS data on its own schedule. This delay is normal.

Can the listing agent force portals to update faster?

No. Once the MLS data is correct, timing is controlled by the receiving websites.

If something is wrong on a portal, where should it be fixed?

Always start with the MLS. Portal issues often resolve after the next data refresh.

Does changing the MLS listing too often cause problems?

Frequent changes can create temporary inconsistencies. That’s why we prefer clean, accurate launches whenever possible.