Domain Tools: WHOIS, Reverse DNS, and Domain Research
Every domain name on the internet has associated registration data stored in a public database. WHOIS lookups query this database to reveal who registered a domain, which registrar they used, when the domain was registered, and when it expires. This information is required by ICANN for most domain extensions and serves important purposes — security researchers use it to identify malicious domains, businesses use it to check domain availability for trademark enforcement, and website owners use it to track domain expiry dates and avoid losing their domain to expiration.
The traditional WHOIS protocol is being replaced by RDAP (Registration Data Access Protocol), which provides structured JSON data instead of raw text. RDAP offers more consistent responses across different registries, supports internationalized domain names, and provides better error handling. IPLocatorTools uses RDAP for WHOIS lookups, giving you clean, parsable registration data including registrar name, registration and expiry dates, domain status codes, and nameservers. Note that many domain owners use WHOIS privacy protection services that hide personal contact details from public queries.
Reverse DNS lookup is the opposite of the more familiar forward DNS lookup. Instead of finding the IP address for a domain name, reverse DNS finds the hostname associated with an IP address using PTR records. This is commonly used by email servers to verify that the sending server's hostname matches its IP address — a critical spam filtering check. Many email systems reject messages from IPs without valid reverse DNS records because spammers rarely configure PTR records properly. Domain-to-IP resolution simply returns the IP addresses that a domain resolves to, useful for verifying that DNS changes have propagated.
The domain availability checker determines whether a domain name is registered or likely available for registration. It checks both DNS resolution (whether the domain has any A or AAAA records) and RDAP registration data. A domain that does not resolve in DNS and has no RDAP registration record is likely available — though the only definitive way to register a domain is through a domain registrar. This tool is useful for brainstorming domain names for new projects, checking if competitors own relevant domains, and verifying that your desired domain is available before approaching a registrar.
Related: Static vs Dynamic IP Addresses →