Reverse WHOIS tools to find domains by registrant data | WhoisXML API

Reverse WHOIS tools and services help you find domain names connected by a registrant identifier

Reverse domain queries via lookups or API calls are useful to identify all domain records that correspond to search terms like a name, an email address, a phone number, etc.

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774 Million+Domains tracked
21.0 Billion+WHOIS records
7,596+TLDs and ccTLDs tracked
52,000+Satisfied customers

Reverse WHOIS queries by registrant data can be done through:


Use our handy lookup web interface to query your search term of interest and get a list of all domain names found in the last 7 days (i.e., for which the term appears in the domains’ WHOIS records). Include and exclude certain terms with the advanced lookup option.

Reverse WHOIS Lookup | WhoisXML API
Reverse WHOIS API | WhoisXML API


You can use Reverse WHOIS API to list linked domain names via API calls. We provide documentation and client libraries to facilitate integration.


  • Establish all known domain name associations with individuals and organizations. Learn more about domain footprints with the consumption model — lookup or API — of your choice.

  • Narrow down your search results by employing filtering parameters to exclude terms that are not relevant to your query.

  • Go with any WHOIS detail you have on hand to run queries via Reverse WHOIS Lookup and make API calls with Reverse WHOIS API. You can use exact-match terms or fuzzy ones for broader results.

  • Results from our lookup tool and API are gathered from the most comprehensive historical WHOIS database on the market with daily updates. All the data returned is parsed, normalized, and consistently formatted.

Product Usage

  • Brand Protection

    Keep an eye out for domain names registered by known cybersquatters and brand infringers by uncovering all web properties tied to public WHOIS details—either current or historical—on record.

  • Threat Actor Profiling

    Using public WHOIS record details as starting points, learn more about threat actors’ current or historical domain footprints and possibly their cybercrime tactics and Indicators of Compromise (IoCs)’ domain infrastructure setup.

  • Competitor Research

    Use our reverse WHOIS solutions to know about upcoming product launches, mergers and acquisitions (M&As), and strategic digital events related to your competitors. Their most recent domain acquisitions can clue you into their future plans.

  • Third-Party Background Checks

    Find out how trustworthy the company you’re hoping to do business with is. Their domains and accompanying WHOIS records may help you confirm claims regarding location, size of operations, and how long a potential partner has been in business.

  • Attack Surface Inventory

    Gauge how large an organization’s potential attack surface is. The entirety of their domain footprint over time obtained via our reverse WHOIS solutions can uncover forgotten domains that could serve as attack vectors.

Reverse WHOIS Overview | WhoisXML API

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