MLS & IDX Integration
RESO Web API and MLS Data Feed Development
RESO Web API and MLS data feed development is building the software that pulls listing data from MLS boards into your own product, keeps it current, and makes it searchable. The RESO Web API is the current standard for that data; older boards may still offer RETS.
It is for proptech companies, agent-website and brokerage platforms, and in-house brokerage teams that need MLS data from one or several boards in the US or Canada inside software they control, rather than a turnkey IDX plugin.
Peregrine builds the pipeline end to end: feed ingestion over the RESO Web API or RETS, normalization across boards, deduplication, a fast search layer, and the IDX website or app on top. We also build and operate our own real estate product, RealFoyer.
At a glance
MLS & IDX Integration at a Glance
| What's delivered | MLS feed ingestion (RESO Web API or RETS), multi-board normalization and deduplication, listing search, and IDX websites with lead capture |
|---|---|
| Engagement model | Fixed-scope projects, monthly retainers, or a combination, agreed after the discovery call |
| How it starts | A 30-minute technical discovery call with an engineer |
| Pricing | Pricing is scoped per project after the discovery call. |
| Related case studies | AI-Powered Multi-Market Real Estate Platform; Scaling a Real Estate SaaS Platform from 5 Agents to 200+ |
Fit
Is MLS & IDX Integration the Right Fit?
A good fit when
- You need listings from one or more MLS boards inside a product you control: a brokerage platform, an agent-website product, a proptech app or an internal tool.
- You use a turnkey IDX vendor and have hit a limit: search you cannot customize, data you cannot store beside your own, or per-agent fees that grow with the business.
- You are moving a working RETS integration to the RESO Web API and search has to stay up while you do it.
Probably not the right fit when
- You want listing search on an existing brokerage website soon, and standard search pages are enough. A turnkey IDX vendor is the faster and cheaper route: IDX vendor or custom build.
- You have no broker or MLS relationship yet, so no path to a data license. Start with access: how to get MLS data access.
What we build
What Does Peregrine's MLS & IDX Integration Service Include?
Peregrine's MLS and IDX integration service builds the full listing pipeline: feed ingestion over the RESO Web API or RETS, normalization across MLS boards, deduplication of cross-listed properties, a fast search layer, and the IDX website or app on top, with lead capture feeding your CRM. We also build and operate our own real estate product, RealFoyer.
Feed ingestion and sync
Scheduled and incremental sync from RESO Web API or legacy RETS feeds, with delta detection so only changed records are processed, per-feed error isolation, and retries so one failing board does not stall the others.
Shown in: Scaling a Real Estate SaaS Platform from 5 Agents to 200+
Multi-MLS normalization
Each board uses its own fields and conventions. We map them into one schema and deduplicate properties listed in more than one MLS, so agents and buyers see a single clean record.
IDX search and property pages
Search with filters, map and geo queries, and auto-suggest, backed by Elasticsearch and a cache, while property detail pages read the latest status so sold listings do not appear as active.
Shown in: Scaling a Real Estate SaaS Platform from 5 Agents to 200+
Agent and brokerage websites
Branded IDX websites for individual agents or whole brokerages from one platform, with lead capture feeding the CRM.
Shown in: Scaling a Real Estate SaaS Platform from 5 Agents to 200+
Natural-language search and valuation
On top of clean MLS data we can add conversational search and automated valuation models; see our AI automation service.
Industries: Real Estate & Proptech · All industries
Timeline
How Long Does an MLS & IDX Integration Project Take?
Peregrine sets the timeline for an MLS feed project after reviewing the boards involved, the feed type each offers and the display and refresh rules in each data license. Data access approval is set by each MLS, not by us. Development then runs in two-week sprints with weekly demos, and every feed is monitored after launch.
Board and license review
We list the MLS boards involved, the feed type each offers, and the display and refresh rules in their data license, since those rules shape the architecture.
Schema mapping
Field-by-field mapping from each board into the normalized schema, including status values, media and open houses.
Pipeline and search
Build the sync engine, search index and cache, then load-test with realistic listing volumes.
Frontend and launch
IDX pages, lead capture and CRM hooks, followed by monitoring of every feed after go-live.
Scope
What Determines the Scope of an MLS & IDX Integration Project?
These are the inputs that change the effort. None needs a final answer before the first call, but each one you can answer makes the estimate tighter.
- Number of MLS boards
- Each board is a separate license, feed, field mapping and set of display rules, so effort grows with every board added.
- Feed type per board
- RESO Web API, legacy RETS or, in Canada, CREA DDF. Each needs its own ingestion code, and older RETS feeds are polled on a schedule.
- License type and display rules
- IDX, VOW and back-office licenses allow different fields, statuses and refresh intervals. The rules shape the schema and the sync.
- Listing volume and freshness
- The number of listings and photos, and how soon a status change must appear, drive sync design, index size and media storage.
- What sits on top
- Search alone is the smallest build. Map search, saved searches and alerts, agent websites, lead routing and valuation each add to it.
- Existing pipeline
- Taking over a feed that already runs means working with its schema and its data-quality problems instead of starting clean.
A sensible first phase
A sensible first phase is one board, end to end: ingestion, field mapping, a search index and a basic results page over real data. It exposes license and data-quality problems early, and adding the second board then shows what multi-board normalization will take.
Cost
What Does MLS & IDX Integration Cost?
Peregrine works on MLS and IDX integration as fixed-scope projects, monthly retainers, or a combination, agreed after the discovery call. Cost depends on the number of boards and what you build on top; MLS data fees go to each board. See MLS and IDX Integration Cost in 2026: Monthly and Yearly Fees by Vendor and MLS for published fees.
MLS and IDX Integration Cost in 2026: Monthly and Yearly Fees by Vendor and MLS
MLS and IDX costs per month and per year in 2026: IDX plugin plans, MLS license fees by board, MLS Grid and Trestle fees, and development rates, all sourced.
Read the guideHow to Get MLS Data Access for Your App
The licenses, broker sponsorship, agreements, platforms (MLS Grid, Trestle, Bridge), fees and compliance rules for getting MLS data into your app, with sources.
Read the guideIDX Vendor or Custom Build: When to Switch
When an IDX plugin is enough, when a data vendor API fits, and when a brokerage or proptech team should build its own MLS pipeline, with sourced costs.
Read the guideRESO Web API vs RETS: What Changes and How to Migrate
What changes when you move an MLS integration from RETS to the RESO Web API: authentication, queries, field names, media and sync, with sources and a checklist.
Read the guideMLS Data Pipeline Architecture: A Reference Design for the RESO Web API
A reference architecture for ingesting MLS data via the RESO Web API: replication, media, normalization, duplicates, compliance checkpoints and failure modes.
Read the guideMLS Data Access in Canada: CREA DDF and Board Feeds
How listing data access works in Canada: CREA DDF channels, rules, API and technology-provider fees, plus board IDX and VOW programs, with sources.
Read the guide15 US MLS Boards: A Data Access Reference
Reference profiles of 15 US MLSs in alphabetical order: who each serves, data delivery, feed types, who may license and where to apply, each fact sourced.
Read the guideEngineering Requirements for a Production-Ready IDX Platform
Testable engineering requirements for an IDX platform: architecture, data reliability, security, performance and operations, each with a way to verify it.
Read the guideSEO, AEO and GEO for Real Estate Websites: What to Build
What a brokerage or proptech site must build to be found in search, answer features and AI answers: indexing, listing lifecycle, schema and crawlers, sourced.
Read the guideWhat It Costs to Build a Real Estate Platform
What drives the cost of a real estate platform: developer rates in the US, Canada and India, MLS data fees, maps and hosting, with every figure sourced.
Read the guideBuilding a Scalable MLS Synchronization Engine
How to build an MLS sync engine: full import, incremental sync, checkpoints, queues, rate limits, backoff, idempotent writes, monitoring and failure recovery.
Read the guideMLS Data Normalization Across Multiple Real Estate Boards
How to normalize MLS data from several boards: RESO field mapping, identifiers, property types, units, media, display flags, provenance and a canonical schema.
Read the guideHandling Deleted, Expired and Sold Listings Correctly
How to handle sold, expired, withdrawn and deleted MLS listings: status mapping, removal signals, reconciliation, index cleanup, HTTP status and license rules.
Read the guideDesigning a Real Estate Search Engine with Elasticsearch
Designing listing search on Elasticsearch: mappings, filters, geo queries, autocomplete, pagination, facet counts, relevance and zero-downtime reindexing.
Read the guideBuilding Map-Based Property Search with Geospatial Queries
How to build map search for listings: viewport and polygon queries, spatial indexes, clustering, list and map sync, URL state, mobile and address display.
Read the guideDesigning Reliable Saved Searches and Listing Alerts
How to build saved searches and listing alerts that do not miss, duplicate or misfire: storage, matching, dedupe, scheduling, unsubscribe and delivery.
Read the guideGetting started
How Does an MLS & IDX Integration Project Start?
A Peregrine MLS & IDX Integration project starts with a 30-minute technical discovery call with an engineer, not a salesperson. Larger builds then begin with a discovery sprint that maps requirements, designs the architecture and produces a written technical plan. Smaller, well-defined tasks can use the quick project form for a scoped estimate.
What to bring to the scoping call
- The MLS boards or markets you need, and which of them you already have a license or broker relationship with.
- Any feed credentials or vendor documentation you hold, and whether each feed is RESO Web API or RETS.
- The license type you have or are applying for (IDX, VOW or back office) and a copy of its display rules.
- What users must be able to do: filters, map search, saved searches, alerts, agent sites, lead routing.
- The systems the listings must feed: CRM, website, mobile app, reporting.
- For an existing integration: what breaks today (stale statuses, slow search, failed syncs) and rough listing counts.
Partial answers are fine. Whatever is missing becomes the first item on the call.
Case studies
Which Case Studies Show Peregrine's MLS & IDX Integration Work?
Two published case studies show Peregrine's MLS and IDX work: the W3|re platform, which unifies four MLS systems (NTREIS, Stellar MLS, ARMLS and REcolorado) and deduplicates cross-listed properties, and a real estate SaaS whose rebuilt MLS sync engine for US and Canadian boards feeds Elasticsearch search for agent IDX websites.
AI-Powered Multi-Market Real Estate Platform
A unified pipeline for four MLS systems (NTREIS, Stellar MLS, ARMLS and REcolorado) that normalizes schemas and deduplicates cross-listed properties.
Read the case studyScaling a Real Estate SaaS Platform from 5 Agents to 200+
Rebuilt the MLS sync engine for US and Canadian boards with delta detection, retry logic and per-feed error isolation, feeding Elasticsearch search for agent IDX sites.
Read the case studyStack
Technology We Use
Related services
Services Often Scoped With MLS & IDX Integration
FAQ
Frequently Asked Questions
What is the RESO Web API, and how is it different from RETS?
Both are standards for transferring MLS data. RETS is the older, XML-based standard; the RESO Web API is its modern replacement, built on RESTful web conventions and the RESO Data Dictionary for field names. Most boards now offer the Web API, and new integrations should use it wherever it is available.
What is the difference between IDX and VOW?
IDX lets a broker display other brokers' listings on a public website under MLS display rules. A VOW (Virtual Office Website) is a password-protected site for registered consumers that can show more data, such as some sold information, under stricter rules. Which one you need depends on your MLS and the data you want to show.
Can you build one data feed from several MLS boards?
Yes. Each board is ingested separately and mapped into one schema, and properties listed on more than one board are deduplicated. Our W3|re case study combines four MLS systems this way.
How current can MLS feed data be?
It depends on the feed and on your MLS rules. Many boards allow frequent incremental updates through the Web API; RETS feeds are usually polled on a schedule. We design the sync around the refresh rate your license requires and your users expect.
Do we need our own MLS data license before development starts?
Usually the broker or the platform applies for data access with each MLS and signs its license agreement. We can help with the technical parts of the application, but the license itself is between your company and the board.
Who owns the IP rights to what Peregrine builds?
You do. Once the work is paid for, the client owns the intellectual property (IP) rights to what Peregrine builds for the project, whether it is delivered as a fixed-scope project, a monthly retainer or a combination of the two.
Questions about the team, contract models and how progress is shown are answered on the services page.
Technical consultation
Talk to an Engineer About MLS & IDX Integration
Tell us what you are building or fixing. Your first conversation is with an engineer, not a salesperson.
- A 30-minute technical discovery call with an engineer, not a salesperson.
- Fixed-scope projects, monthly retainers, or a combination, agreed after the call.
- Small, well-defined tasks get a scoped estimate. We reply within 1 business day.
Prefer to pick a time? Book a call on Calendly
