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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →To prevent unauthorized scraping of MLS listings, start with the rules and data license for the specific MLS feed, then restrict access to authorized users and approved purposes, monitor for bulk extraction, and apply reasonable technical protections. MLS requirements differ: there is no universal security checklist or API rate limit that applies to every IDX or VOW site.
Start with the MLS rules and data license
Before changing a website, identify which listing data it displays, which agreement or license governs that data, and which obligations apply to the Participant, site operator, and technology vendor. IDX and VOW arrangements are not interchangeable, and a rule for one MLS or jurisdiction should not be assumed to apply everywhere.
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For covered VOWs, the U.S. Department of Justice Antitrust Division policy says a Participant’s VOW must use reasonable efforts to monitor for and prevent scraping or other unauthorized access, reproduction, or use of the MLS database. Stellar MLS has similar language in Article 20.05 and identifies firewalls as an example of appropriate security protection. Those are concrete examples, not a universal checklist for every MLS.
Check the current local rules, vendor instructions, and data-use agreement for required safeguards, reporting routes, and any limits on access. NAR guidance directs MLSs to publish instructions for requesting feeds; the local MLS’s requirements govern the actual authorization process.
Use an authorized feed or API—not an assumed public data source
For a legitimate integration, request access through the MLS or its designated technology provider, accept the applicable licensing and data-use terms, and use only the credentials and scope granted. RESO standardizes data-exchange interfaces; it is not the provider of listing data. As RESO puts it, “RESO does not provide MLS real estate data.” Access credentials and connection instructions come from the local MLS after the recipient meets its requirements.
Keep credentials restricted to the service and people authorized under the data arrangement. Configure authentication and access controls appropriate to the site’s rules, and do not expose bulk exports or data endpoints to unauthenticated visitors unless the MLS has expressly authorized that access. These are practical ways to support the obligation to prevent unauthorized access; the cited sources do not prescribe one technical design for all sites.
Apply technical protections without blocking legitimate use
Use controls that make unauthorized bulk extraction harder while preserving ordinary consumer browsing and permitted access. The governing MLS rules and license—not a generic security recipe—determine what is required. Stellar MLS’s Article 20.05 gives firewalls as an example and says required protections must not impose obligations greater than those concurrently employed by the MLS; that clause is specific to Stellar MLS and should not be treated as a rule for other organizations.
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- Use authentication and authorization to limit data access to approved users, services, and purposes.
- Apply firewall or web-application firewall protections where appropriate and consistent with the applicable MLS requirements.
- Keep public pages and authorized search or display functions working as permitted by local rules; tune anti-bot controls to avoid disrupting normal visitors.
- Protect credentials and review who can use them, especially where a vendor or multiple systems are involved.
Do not assume that blocking every automated request is required or desirable. The older CRMLS rules cited in this context say IDX security efforts need not prevent recognized search-engine indexing, but that is an older, local example. Verify current local policy before relying on it.
Monitor for extraction and follow the local reporting process
Monitoring helps distinguish expected consumer use from suspicious bulk access. Look for patterns such as unusually high request volume, repeated retrieval of listing records, or activity inconsistent with the service’s intended use. Investigate anomalies against expected traffic and the authorized feed’s normal operating pattern rather than treating one unusual request as proof of a violation.
MLS rules can specify what to do when scraping is suspected. MLS GRID, for example, has requirements involving monitoring and reporting suspected scraping and evidence to the relevant data authority. Confirm the applicable authority, notice channel, evidence requirements, and timing in your own MLS documents. If the suspected conduct involves another Participant or Subscriber, consult the MLS complaint and notice procedures before making legal claims.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Are MLS API rate limits the same everywhere?
No. Rate limits are set by the relevant MLS or API documentation, not by a universal RESO threshold. A CLAW MLS API guide, whose documentation footer is dated 2023, gives this example:
| CLAW MLS API limit | Documented value |
|---|---|
| Requests per second | 2 |
| Requests per hour | 7,200 |
| Download volume per hour | 4 GB |
| Requests per 24-hour period | 40,000 |
Those limits are specific to the CLAW documentation and are not safe defaults for another MLS. Obtain current limits and any download or use restrictions from the relevant MLS or its designated provider, then configure integrations to stay within them.
Keep authorized display separate from redistribution
Permission to display listing data does not grant permission to copy or redistribute it without limits. NAR’s reproduction policy limits MLS information to Participants and affiliated licensees authorized to access it, while allowing only specified limited copies for prospective purchasers. Follow the policy and local license terms for the particular data and audience; do not treat an authorized IDX or VOW display as blanket permission for bulk reuse.
A practical implementation sequence
- Identify the governing documents. Map each MLS data source to its current rules, license, feed/API agreement, and vendor terms.
- Confirm who and what are authorized. Record the approved users, services, purposes, display scope, and access method.
- Request and configure approved access. Use credentials and instructions supplied by the local MLS or designated provider; apply its current rate and use limits.
- Restrict and protect access. Limit credential use, require appropriate authentication, and deploy firewall or other controls consistent with local requirements.
- Monitor and review anomalies. Establish expected traffic patterns, review signs of bulk extraction, and retain relevant evidence under your operational and contractual requirements.
- Escalate through the correct channel. Follow the MLS’s reporting or complaint process for suspected misuse and verify local notice deadlines rather than assuming a universal timeline.
These steps are operational guidance, not legal advice. For a suspected violation or a conflict between a technical control and an MLS requirement, use the applicable MLS’s official process and consult qualified counsel where appropriate.
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