The WhoisXML Reverse IP/DNS API gives developers the ability to discover all connected domain names hosted on the same IP address. This allows detecting suspicious or dangerous sites, preventing overblocking, and conducting penetration testing. The API can also be used for SEO and brand protection purposes and to improve web hosting reputation. It covers close to 1.5 billion domains and subdomains with more than 1.2 billion IPv4 addresses updated daily. Both free and paid subscription plans are available. The free plan is limited to 100 queries per month.