Constellation1 serves MLS data over the RESO Web API. We sync it into your WordPress, Laravel or custom site and keep it current every 2 to 3 hours.
POST /oauth2/token Basic$filter=ModificationTimestamp gt {last}@odata.nextLinkMember, Office, OpenHouseMedia ordered by OrderConstellation1 delivers listings, members, offices and open houses. Pulling them into your own site, and keeping them right, is the work. Constellation1 was one of the feeds on a multi MLS platform we built and ran from 2018 to 2025.
Constellation1 is a real estate software company and part of Constellation Software Inc. It sells websites, CRM, transaction and data products to brokerages, MLSs and technology partners, and says it has worked in real estate since 1995.
Its listing data work sits with Constellation Data Labs, a related company in the same group that handles listing aggregation and data services. Constellation1 says its technology connects to hundreds of MLSs across the United States and Canada, and the listing data is mapped to the RESO Data Dictionary.
Unlike Trestle or Bridge, Constellation1 does not publish its API documentation openly. API access is offered to qualified technology and data partners, and the details come with that access.
Constellation1 coordinates the licensing, but the MLS still grants it. Expect to talk to the company before you see any documentation.
API access is for qualified technology and data partners, so the first step is a conversation about what you are building.
Constellation Data Labs says access generally needs approval from an MLS member broker. If you are the broker, that is you.
The MLS grants the licence and the agreements are signed. Constellation Data Labs offers to coordinate this step.
Once licensed, you receive credentials and the API documentation for your feed.
The sync is built and checked against your feed before your pages read from it.
Constellation1 shares its API docs with approved partners, not publicly, so confirm these against the documentation you receive.
01Listing data is mapped to the RESO Data Dictionary, so standard fields such as ListPrice and StandardStatus mean the same as on other feeds.
02The feed delivers listings with members, offices and open houses. Open houses come as their own records and are matched back to their listings.
03Access uses OAuth client credentials sent in a Basic header. The token is cached and refreshed when it expires.
04Changes are pulled by modification timestamp, so only listings that changed since the last run move.
05Constellation Data Labs also lists GraphQL APIs, webhooks, event streams, batch files and cloud data shares. Which one you get depends on your agreement.
06A regular check of which listings are still in the feed catches what went off market. The audit confirms how your feed signals a removal.
Things that only show up once a feed has run for a few months. We learned them on a multi MLS platform we built and ran from 2018 to 2025.
The token is requested with a Basic header, cached, and refreshed on expiry so long pulls finish.
Open houses come from a separate resource and are matched back to their listings, which get a flag the site can filter on.
Each MLS on Constellation1 has its own field quirks. They live in small filter classes, so one board's fix never touches another.
Off market listings are purged daily. If the feed returns too few IDs, the purge is skipped and we get an alert.
The client ID and secret stay in server side config, and the token is cached in the database between runs. The sync runs from a server cron job, so a slow pull never holds up a page. Open houses are stored against their listings, so a theme can filter on them.
Queued jobs on the scheduler handle listings, rosters and open houses on separate schedules. The token sits in the cache with its expiry and is refreshed before long pulls. Each MLS on the feed gets its own small parser class on top of the shared one.
If your agreement gives you webhooks or a data share instead of an API, the sync changes shape: it receives or loads data rather than polling for it. The output is the same listing schema, so your pages read listings the same way either way.
Your listings never go blank. The new sync runs beside whatever feeds the site today, and we only switch when the two match.
We check your Constellation1 access, your platform and what the site needs to show.
It fills its own tables while your current listings stay up.
Counts, statuses, photos and rosters checked against the feed.
Pages read from the new sync. The old plugin or script is removed.
Constellation1 aggregates many MLSs and coordinates the licensing, which suits brokerages and franchises that cover several markets. Trestle, Bridge and MLS Grid publish their API rules openly, which makes them easier to assess before you commit.
The choice comes down to how many MLSs you need, the fees on each route, and whether you want one company handling the licences. The audit sets out the options your MLS gives you.
Your site's address, what it runs on, and which MLS or feed you have access to.
Access, fields, photos, rosters, and how your platform stores listings.
What syncs, how often, what shows where, and a fixed price for the build.
If you go ahead, the $499 comes off the integration.
We are an independent developer. We are not affiliated with, or certified by, any MLS or data provider named on this page.
Send the site's address and the feed you have access to. The audit gives you a written plan and a fixed quote.