4 Questions to Ask About RESO Web API Before You Pay for IDX
You've got two free plugin tabs open. Maybe a theme's built-in listing page too. The feature lists look similar enough that you've been reading them back and forth for 20 minutes. None of the three pages answers the one question that actually matters before paying for an IDX add-on: whether the MLS connection speaks the RESO Web API or the older RETS protocol the industry has moved on from.
These four questions cut through the sales copy before you spend anything.
What is the RESO Web API?
The RESO Web API is the current standard for real estate listing data exchange, published by the Real Estate Standards Organization. It replaced the older RETS protocol after RESO retired RETS from its certification program. An IDX add-on that speaks the RESO Web API connects to your board's MLS data through a modern, maintained interface. One still built on RETS connects through a protocol the industry has officially moved on from, on a timeline your board controls, not the add-on vendor.
Question 1: Is that RESO Web API, or the older RETS protocol the industry retired?
Real estate boards used to distribute listing data over RETS (Real Estate Transaction Standard), and a lot of IDX add-ons were built around it. The problem now is that RESO has retired RETS from its certification track. Boards are phasing it out on their own schedules, which the add-on vendor doesn't control.
An IDX add-on built on RETS can go dark the day your board drops RETS access. That day varies by board, but it's coming for every board that hasn't already cut it. Some new boards have never offered RETS at all.
What to look for: the add-on's documentation should say "RESO Web API" explicitly. Not "MLS integration" or "IDX ready" or "industry-standard protocols." Vague language on this point usually means RETS, because a vendor who speaks the RESO Web API tends to say so. If you can't find a clear statement in the docs, ask the vendor directly which protocol version their connection uses. Ask for it in writing.
Question 2: Do your listing pages live on your domain, or inside a vendor iframe?
Some IDX products serve listings as an iframe loaded from the vendor's own subdomain. The page looks like part of your site. The URL in the address bar says otherwise.
Traffic to an iframe widget builds the vendor's domain, not yours. Search engines index those URLs under the vendor's property. Backlinks pointing at those listing pages strengthen the vendor's site. When you stop paying, the pages disappear, because they were on the vendor's infrastructure the whole time.
A WordPress plugin that creates actual pages on your own installation is different. Those URLs resolve on your domain from day one. Your analytics sees the traffic. Search index entries build under your domain. If you ever switch plugins, the URLs belong to you.
Ask the vendor to show you a live customer example URL. If the domain in that URL points to the vendor's subdomain rather than a customer's own site, you have your answer.
Question 3: What does your board charge for the feed, before any plugin or add-on enters the picture?
This is the number most buyers don't have when they start comparing add-on prices, and it's the one that changes the math most.
The board's data feed fee is a completely separate line item from any plugin or add-on price. Your local board sets it, or a regional or national data aggregator does. It exists whatever the software connecting to it costs, a free plugin or a monthly subscription.
Some boards include feed access in standard member dues. Others charge a monthly or annual data access fee on top of membership. Some route data through aggregators that have their own pricing, negotiated separately. None of that appears on any plugin pricing page, because the plugin vendor genuinely doesn't control it.
Get the board's number before you evaluate any add-on. Call or email their technology desk. Ask what they charge for an MLS data feed connection for a WordPress site using the RESO Web API. Write it down. Then add it to the add-on price. That combined figure is what IDX actually costs you per month or per year.
A low add-on price paired with a high board fee isn't the bargain it looks like. A higher add-on price with no separate board fee might be cheaper in total. You can't compare until you have both numbers.
Question 4: What do you still hold if you cancel the add-on subscription?
This is the portability question. Most people skip it until they need the answer at the worst possible moment.
When a paid IDX add-on subscription ends, your listing pages can go one of three ways. In the best case, the pages stay on your site but stop updating because the feed stops while the WordPress posts remain. In a middle case, the pages go to a placeholder state but the URLs survive and you can rebuild from there. In the worst case, the add-on removes its content on deactivation and those pages are gone.
Ask the add-on vendor which of those describes their deactivation behavior. Look for a written statement in the documentation. If it isn't there, ask before purchasing. The answer tells you whether you're building a site asset that outlives the subscription or renting a data display that disappears with it.
This matters especially for any listing pages you've spent time optimizing, because that SEO work is wasted if the URLs vanish when you cancel.
Which of the tabs you've been reading for 20 minutes names the connection standard, confirms listing pages resolve on your own domain, and states plainly what stays on your site when you cancel? FW Real Estate is a free plugin that answers the first two directly. It creates real pages on your own install, not inside a vendor iframe. The MLS/IDX add-on connects over the RESO Web API, not the RETS protocol the industry has moved on from. If you cancel the add-on, the listing posts stay on your site; the live feed stops but the pages don't disappear with it. That's the portability question answered in writing, before you pay for anything. Install it, keep it, and build the listing infrastructure that belongs to your domain from day one. Check the plugin against your four questions →
Ask the add-on vendor the same four questions before you pay
The four questions apply to any IDX add-on. That includes ours.
FW Real Estate is a free WordPress plugin that creates real listing pages on your own domain, not inside a vendor iframe. You can install it directly from wordpress.org/plugins/fw-real-estate/. The MLS data connection is a paid add-on to that free core, not something built into the base plugin. We name it as an add-on in everything we publish about it.
Before paying for the MLS/IDX add-on, run the same checklist: Does it speak the RESO Web API? Do the listing pages resolve on your domain? What does your board charge for the feed? What stays on your site if you cancel?
The free plugin handles everything short of a live board feed. Property listings you add manually, custom fields for your market, search and archive pages, single-property pages, all design work through your existing WordPress theme. The MLS/IDX add-on sits on top of that once you've confirmed the feed economics make sense for your setup.
If you'd rather hand the whole setup to someone, Fastw3b offers an MLS/IDX Integration Setup service for agents and agencies who want it running without touching the settings themselves.
Frequently Asked Questions
What is the difference between RETS and RESO Web API?
RETS (Real Estate Transaction Standard) was the data exchange protocol MLS boards used for roughly two decades. The Real Estate Standards Organization (RESO) retired RETS from its certification program and replaced it with the RESO Web API, built on OData. RESO Web API connections are more standardized and easier to maintain, and new boards often don't offer RETS at all.
Does every MLS board charge a separate data feed fee?
Yes, though the amount varies. Some boards include feed access in standard membership dues. Others charge a monthly or annual data access fee, or route feeds through a third-party aggregator with separate pricing. This fee is set by your board or aggregator, not by the plugin or add-on vendor, and it exists regardless of what software you use to connect.
What does "listing pages on your own domain" actually mean for SEO?
It means the URL in the browser address bar shows your domain name. Pages that resolve on your domain accumulate search index entries and backlinks for your site. Pages served in an iframe from a vendor's subdomain look like yours but register under the vendor's domain in search results, so the SEO value builds their asset, not yours.
Can I use FW Real Estate without the MLS/IDX add-on?
Yes. The free plugin lets you add and manage property listings manually, set up search and archive pages, create custom fields for your market, and build the full listing experience through your WordPress theme. The MLS/IDX add-on is what connects to a live board feed. You can install and use the plugin without purchasing the add-on.
What happens to my listing pages if I cancel the MLS/IDX add-on?
This depends on the specific add-on and how it handles deactivation. Ask the vendor and look for a written statement in the documentation before purchasing. The key question: does the add-on remove its listing posts on deactivation, or do the WordPress pages remain even if they stop updating? The answer determines whether you're building durable site content or renting a data display.
FW Real Estate is a free plugin on wordpress.org. There's nothing to buy before you install it, no account to create, and a fresh install contacts nothing outside your own server. The free download includes custom property fields, filterable layouts, a search that cascades country to region to city, detail pages with a photo gallery, and rentals alongside sales with their own lease terms and pricing.
The MLS/IDX add-on is a paid add-on sold separately. It connects over the RESO Web API, CREA DDF, and the UK and European portal feeds. Your board or data provider's feed access fee is a separate cost, billed directly to you in your own name, not by Fastw3b, and it varies by board and region. Pricing for the MLS/IDX add-on is at fastw3b.com/products/fw-real-estate.
You can see the full add-on range running at realestatewordpress.fastw3b.com, though that demo shows more than the free plugin installs.
