IDX Integration and MLS API Integration Done Right

What is the difference between IDX and an MLS API?

IDX (Internet Data Exchange) is the set of rules that lets a participating broker display other brokers' listings on their site. An MLS API is the technical way to get the data. In practice you need both: a license or approval from your MLS to use the data, and a feed such as the RESO Web API that delivers it.

Many agents buy an IDX plugin or hosted IDX product. That works for a basic search page. A custom integration is the right choice when you need listings inside a CRM, a custom search experience, saved search alerts tied to your own database, or analytics the plugin cannot give you.

What is the RESO Web API and how does it replace RETS?

The RESO Web API is the standard for MLS data access. It is an HTTP API based on OData, authenticated with OAuth 2 bearer tokens or a server token, and its field names follow the RESO Data Dictionary so Bedrooms or ListPrice mean the same across boards. RETS, the older standard, used a different protocol and is being retired MLS by MLS.

RESO's leaderboard shows no single industry sunset date. It lists projected completion dates for individual MLSs, such as 12/31/2026 for one and 6/30/2027 for another, while most show TBD. Building on RETS today means a rebuild later.

Authentication details differ by MLS and by the platform that serves its feed, such as a vendor that hosts the Web API for several boards. Some issue a server token, others use OAuth 2 client credentials, and each sets its own request limits. Ask your MLS which platform it uses and what limits apply before sizing the sync schedule.

How should listing data be stored and refreshed?

Querying the API on every page view is slow and can breach rate limits. Most builds replicate: pull the full set once, then fetch changes by ModificationTimestamp on a schedule, and store them in your own database. Search runs against your database, so pages load quickly.

Replication has traps. Listings go off market and must be removed on time, which means handling status changes and deletions, along with new records. Media (photos) arrive as separate URLs with their own rules about hotlinking and caching. Your MLS may restrict how long and in what form you may store data.

• Incremental sync on ModificationTimestamp with a periodic full reconciliation
• Status handling for Pending, Sold and Withdrawn, per your MLS's display rules
• Photo handling that follows your license
• Alerting when a sync run fails or returns an unusual record count

What display rules usually apply?

MLS rules commonly require listing broker attribution, a disclaimer with data refresh time, and limits on showing sold data or certain fields. Rules vary by board, so Vascoh reads your MLS rules and encodes them into templates and field filters rather than relying on a generic default.

How does MLS data connect to your CRM and AI tools?

Once listings sit in your own database, they can feed property alerts in a CRM, listing-based chatbots that answer from real fields, and reporting. Pushing a matched-listing alert into Follow Up Boss, kvCORE or a custom CRM is an API call away. Vascoh builds the connection so alerts reference the current listing record.

Search quality is the part visitors notice. Filters for price, beds, baths, property type and map bounds need indexes on those columns, and map searches need a geospatial query against latitude and longitude. Sort orders such as newest listings depend on the same timestamp fields that the sync uses. Saved searches add a scheduled job that matches new and changed listings to each subscriber and sends an alert through your CRM or email system. Vascoh builds these on your replicated data so response time does not depend on the MLS server.