What IDX is
IDX, short for Internet Data Exchange, is the arrangement that lets brokers display other brokers’ listings on their own websites. Multiple listing services, or MLSs, control the data and set rules about who may display it, what must be shown and how. Real estate sites that show a searchable property inventory rely on an IDX feed or a product built on one.
Why the choice matters
Listings are the main reason visitors come to a real estate site, and the way they are delivered affects search visibility, speed, user experience and your ability to capture leads. A site that merely embeds a third-party widget may look fine yet add little organic value.
Integration options
| Option | How it works | Strengths | Weaknesses |
|---|---|---|---|
| Iframe or widget | A search tool from a vendor is embedded in your page | Quick and cheap to set up | Content often not attributed to your domain, limited design and SEO value |
| WordPress IDX plugin | A plugin pulls data and renders pages on your site | Moderate cost, indexable pages possible | Plugin quality varies, performance can suffer |
| Hosted IDX platform with a branded site | A vendor provides both site and search | Integrated, includes lead tools | Less flexibility, vendor lock-in |
| Direct feed via RESO Web API | Your developers pull listing data and build pages | Full control of design, SEO and data | Higher cost, requires engineering and MLS approval |
| Aggregator data service | A third party combines feeds from several MLSs | Easier multi-market coverage | Fees, and still subject to MLS rules |
Many MLSs are migrating from older RETS feeds to the RESO Web API, so ask about current feed standards.
MLS rules to review
- Who is eligible to display listings and under what membership.
- Required disclaimers, attribution and logos.
- Restrictions on how long data can be stored, how often it must refresh and whether sold listings may be shown.
- Rules about what fields may be displayed.
- Restrictions on scraping, resale and use for other purposes such as AI features or automated valuation.
- Marketing restrictions, such as showing another broker’s listing attribution.
Rules differ by MLS and region, so read your agreement. Violations can lead to fines or loss of access.
SEO for listing sites
- Indexable pages. Search engines need to see listing and neighborhood pages as part of your domain, not just inside a script or iframe.
- Thoughtful scale. Thousands of near-duplicate listing pages offer little value. Focus on neighborhood, community and property-type pages with original content, market insights and local expertise.
- Handling expired listings. Decide whether to keep, redirect or mark them, based on MLS rules and user value.
- Structured data. Use appropriate markup for real estate listings and local business information.
- Fast pages and images. Listing photos are heavy. Use responsive images and lazy loading.
- Local content. Guides on neighborhoods, schools, transportation and market conditions build authority.
Competing with large national portals on listing pages alone is difficult. Differentiate with local knowledge and content.
Features users expect
- Map and list search with filters for price, bedrooms, property type and more.
- Saved searches and email alerts.
- Favorite properties.
- Mobile-friendly galleries and virtual tours.
- Mortgage calculators and neighborhood data.
- Easy contact and showing request buttons.
Use the Fair Housing standards when writing neighborhood descriptions, avoiding language that steers by protected characteristics.
Lead capture and follow-up
Some sites require registration after a few views. This increases leads but can frustrate visitors, so test the balance. Connect forms and alerts to your CRM and follow-up system, with consent for emails and texts. See the lead follow-up article for details.
Performance and accessibility
Map-based search is script heavy. Test on mid-range phones, defer non-critical scripts and keep layout stable. Provide keyboard-accessible controls and alternatives to map-only interaction.
Questions to ask vendors and developers
- Which MLSs do you support, and how do you handle approvals?
- Are listing pages hosted on my domain and indexable?
- How fast are updates?
- What happens to my data and pages if I leave?
- How do you handle compliance requirements and display rules?
- What are the performance results for typical search pages?
FAQ
What is IDX?
It is the framework and data feed that allow brokers to display MLS listings on their own websites under MLS rules.
Are iframe IDX tools bad for SEO?
They generally provide little search value to your domain because the content lives elsewhere. They can still help with convenience and speed to launch.
Can I build a custom IDX site?
Yes, using an MLS-approved feed, often through the RESO Web API, but it requires development and compliance work.
Do I need MLS approval?
Yes. You need access rights and must follow display rules set by the MLS.
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