SimplyRETS vs Spark API: a REST layer on your own MLS feed or MLS data for Flexmls apps
SimplyRETS is a developer API and WordPress plugin that turns your own MLS's RETS or RESO Web API feed into a simple REST listings API. FBS's Spark API and RESO Web API give authorized applications access to MLS data on the Flexmls/Spark platform.
The short answer
- SimplyRETS: An affordable, simple REST layer for an agent or brokerage that already has its own MLS data feed.
- Spark API: Apps built for agents, brokers or MLSs that use Flexmls, where the MLS member authorizes access.
Side by side
| SimplyRETS | Spark API | |
|---|---|---|
| Searches | Listings from the MLS feeds you connect: active, under contract, pending and closed; residential, condo, rental, multifamily, commercial and land, plus open houses. | MLS listings (and, for VOW apps, sold data) from participating MLSs, within the roles each MLS grants. |
| Returns | Listing records with property details, photos, and listing agent and office information when the MLS feed supplies it. | MLS listing records in Spark or RESO Web API format. |
| Before the first call | RETS or RESO Web API credentials from your MLS; whether you must be an agent or broker depends on the MLS. | A free developer account, then an MLS data plan or an MLS member who authorizes your app. |
| Free | Free demo API keys with sample data; no free trial with live data. | Developer account sign-up is free. |
| Paid | Basic plan $49 a month, plus a one-time $99 fee per MLS connection. | $50 a month for each MLS you access, once you have data from your first MLS (MLS data plans may set their own terms). |
| Acting on a result | Listing agent and office contact details come with each listing when the MLS feed has them, and some MLSs require showing them. | Not stated on its pages |
| Limits on keeping or showing results | Only listings flagged for IDX display are served, and you must follow the display rules (e.g. last-updated disclaimers) set by your MLS. | No storing MLS content except temporary caching for performance, unless your key permits replication; MLS display rules and license terms apply. |
| Coverage | Whatever MLS you connect (US); no fixed national coverage. | Participating MLSs on the FBS platform; no list or count on its pages. |
| MCP server | No official server listed | No official server listed |
Where Openpath fits
Openpath has no homes listed yet. Owners and landlords can list a home for rent or sale on Openpath today, free, and agents will find it through the same search as jobs and businesses. Get listed.
Questions people ask
What do I need before I can use SimplyRETS?
RETS or RESO Web API credentials from your MLS; whether you must be an agent or broker depends on the MLS.
Is SimplyRETS free?
Free demo API keys with sample data; no free trial with live data.
What do I need before I can use Spark API?
A free developer account, then an MLS data plan or an MLS member who authorizes your app.
Is Spark API free?
Developer account sign-up is free.
Sources
Every line about another company comes from its own pages. Prices and terms change, so check the source before you rely on one.
SimplyRETS, read on October 15, 2026:
- simplyrets.com: “These are our demo API keys, you can use them!”
- simplyrets.com: “Each RETS or RESO Web API connection requires one time $99 connection fee.”
- simplyrets.com: “Get RETS or RESO Web API credentials from your MLS”
- simplyrets.com/faq: “This is dependent on the MLS area you want to connect to.”
- docs.simplyrets.com/topics/fields-and-features-for-idx-compliance: “In some cases it may be required that you show the contact information for the listing agent and/or listing office.”
- docs.simplyrets.com/topics/fields-and-features-for-idx-compliance: “in many areas it’s required to show the timestamp of when the data was last updated in a disclaimer.”
- simplyrets.com: “Basic $ 49 /mo”
- simplyrets.com/faq: “We don't currently offer a free trial period with live data”
Spark API, read on October 15, 2026:
- sparkplatform.com/docs/overview/api: “The Spark API allows authorized MLS members to request data through developer applications”
- sparkplatform.com/docs/overview/api: “When IDX applications are purchased, the MLS member must authorize that application to access their data.”
- sparkplatform.com/docs/overview/faq: “It’s free to sign up for a Spark API developer account.”
- sparkplatform.com/docs/overview/faq: “Once you have access to data from your first MLS, API access costs $50/mo for each MLS you can access.”
- sparkplatform.com/docs/terms_of_use/developer_agreement_and_terms_of_use: “except for temporary caching purposes necessary for performance enhancement”
- sparkplatform.com/docs/terms_of_use/developer_agreement_and_terms_of_use: “Compliance with MLS Rules and License Terms regarding MLS Content”