How IDX Works: MLS Feeds, Display Rules, and Compliance Explained

This post covers the mechanics behind it: where the data comes from, who decides what appears on your site, the display rules your MLS enforces, and how IDX compares with VOW. If you’re still deciding whether you need an IDX website at all, start with our complete guide to IDX websites.

What happens between the MLS and your website?

Every listing on an IDX site goes through the same path before a buyer sees it:

1. A listing agent enters the property into the MLS. That record is the source data: price, status, photos, features, and the listing brokerage.
2. The listing is included in IDX by default. Under typical MLS rules, a participating broker’s consent to have their listings shown on other participants’ sites is presumed unless the broker opts out. Sellers can also opt out (more on that below).
3. Your brokerage authorizes IDX display. IDX is a broker-level permission. Agents can display IDX listings on their own sites with their broker’s consent.
4. The MLS delivers the data to your website vendor. The vendor is licensed to receive the feed for your market and pulls it through the MLS’s data connection.
5. Your vendor processes and publishes the listings. The platform turns raw feed data into searchable listing pages and refreshes them on a required schedule. Many MLS rule sets require IDX data to be refreshed at least once every 12 hours.
6. A visitor searches, saves, and registers. The listing data belongs to the MLS and the listing broker. The lead belongs to you.

The rest of this post covers what happens at each step.

What is an IDX feed, and where does the data come from?

An IDX feed is the stream of listing data your MLS sends to your website vendor: the subset of each listing record that’s approved for public display, delivered on a recurring schedule so your site stays current.

Internet Data Exchange is the set of rules and permissions. The feed itself moves through a technical connection between the MLS and your vendor, and that connection has changed in recent years.

RETS (Real Estate Transaction Standard) was the industry’s data transport protocol for more than 20 years. The Real Estate Standards Organization (RESO) has since deprecated RETS and replaced it with the RESO Web API, a modern API-based standard. According to RESO’s Web API Transition Leaderboard (June 2026 report), at least 90% of MLSs have RESO-certified Web API services, and MLS feeds that have finished converting cover about 62% of U.S. subscribers, up from less than 5% of the industry in 2021.

The RESO Data Dictionary standardizes field names across MLSs, so “list price” or “bedrooms” means the same thing from one market to the next.

Two practical takeaways for agents and brokers:

• You don’t manage the feed. Your vendor handles the connection, the credentials, and the switch from RETS to the Web API.
• Fields still vary by market. An IDX feed includes only a subset of the full MLS record. Core fields like price, beds, baths, status, and property type are standard. Market-specific fields, like pools or subdivision names, depend on what your MLS provides. A vendor can’t add fields your MLS doesn’t supply.

Who controls which listings appear on your site?

Four parties have a say in what appears on your site, and that explains most “why isn’t this listing on my site?” questions.

The listing broker. A participating broker can refuse IDX display of their listings, either across the board or for individual listings. MLS rules typically make this reciprocal: a broker who opts out across the board can’t display other participants’ listings through IDX either.

The seller. A seller can tell their listing broker to keep the listing, or just the property address, off the internet entirely. A seller can also ask that comments, reviews, and automated valuations (AVMs) be turned off on their listing. Your site must honor those requests.

You. Decide which listings to display, but only by objective criteria such as geography, list price, property type, or listing type. You can also connect your site to your local MLS with filters that feature your own office’s or your agents’ listings. You can’t selectively hide individual competitors’ listings.

Your MLS. The MLS decides which listing statuses and data are eligible for IDX at all. Many MLS rule sets prohibit displaying expired, canceled, withdrawn, and coming-soon listings through IDX. Sold data depends entirely on the MLS: some include it and some don’t. In some regions, such as parts of Canada, sold data can’t be displayed publicly.

What are the IDX display rules?

Each MLS sets its own IDX rules. REALTOR®-affiliated MLSs generally base theirs on the National Association of REALTORS® model IDX policy, then add local requirements. The specifics vary, but these requirements are common:

Your MLS enforces these rules, so the safest approach is a platform that applies them automatically instead of relying on you to check every page.

Can agents show IDX listings on their own websites?

Yes, with conditions. IDX permission belongs to the participating broker. Agents and non-principal brokers can show IDX listings on their own sites with their broker’s consent and under the broker’s control, subject to state law. Many MLSs also require a signed license agreement before an agent’s site can receive the feed.

In practice, this works best when the brokerage’s site and its agents’ sites run on the same platform, because compliance, branding, and lead routing stay consistent across all of them.

What’s the difference between IDX and VOW?

IDX and VOW (Virtual Office Website) both put MLS data on a broker’s website, but they’re built for different relationships with the consumer.

For most agents and teams, IDX is the right tool. It’s public, so it can rank in search and bring in new visitors. VOWs can show more data, but they sit behind a login, which makes them a tool for serving existing clients rather than attracting new ones.

What happens after a visitor searches?

This is where IDX turns into business. A visitor searches listings on your domain, saves a search or asks for more detail, and registers. That contact should go straight into your CRM, with their search behavior attached, so follow-up starts right away.

The data rules above cover the listings. They don’t stop you from owning the relationship with the person who found that listing on your site. That’s the main reason IDX is worth doing well.

What should you ask an IDX vendor?

When you compare IDX website platforms, these questions show quickly whether a vendor handles IDX well:

• Which MLS feeds do you support in my market, and is my MLS’s feed on the RESO Web API?
• How often does my site refresh from the feed? Ask for the actual interval, not “real time.”
• How do you apply my MLS’s display rules? Brokerage credit, disclaimers, confidential fields, and seller opt-outs should be handled automatically.
• Do you support sold data in my market? If so, how long does it stay visible?
• Can I filter by office or agent to feature my own listings?
• Can I request new fields when my MLS adds them?
• How do you handle duplicate listing content? The same MLS listings appear on many sites, so ask how the platform keeps your pages from being treated as copies.

Frequently asked questions about IDX

How often do IDX listings update?

It depends on your MLS and your vendor. Many MLS rule sets require IDX displays to refresh at least once every 12 hours, and many platforms refresh more often than that. Ask your vendor for the actual sync interval in your market.

Why isn’t a specific listing showing on my IDX site?

The most common reasons are that the listing broker or the seller opted out of IDX display, the listing’s status isn’t eligible for IDX under your MLS rules (for example, coming soon or withdrawn), your MLS excludes that listing type from its IDX feed, or the listing changed after your site’s last refresh.

Can I show only my own listings on my website?

Yes. You can filter your IDX display using objective criteria, including by your office or agent ID, to feature your own listings. You can’t selectively hide individual competitors’ listings from an otherwise complete search.

Can I edit the listing descriptions on my IDX site?

No. You can’t modify other participants’ listing information. You can add information from other sources, such as your own neighborhood content, as long as you clearly identify the source.

Is IDX the same as listing syndication?

No. IDX lets MLS participants display each other’s listings on their own websites under MLS rules. Syndication usually means sending listings to third-party sites such as national portals, under separate agreements.