WHOIS Protocol
A query and response protocol widely used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name or an IP address block. Traditionally operates over TCP port 43.
Educational Reference
WHOIS & Domain Term Glossary
Confused by registry jargon? Browse our dictionary of standard industry terms to understand how domain databases, crawlers, and registrar records operate.
Core Protocols
RDAP (Registration Data Access Protocol)
The modern successor to the WHOIS protocol. RDAP delivers domain registration data in standardized JSON format over secure HTTP (HTTPS), allowing for better localization, structured queries, and secure access controls.
Port 43 WHOIS
The default TCP port designated for raw WHOIS text queries. Modern crawlers and clients connect to port 43 of registry or registrar servers to fetch plain-text WHOIS data records.
Zone Files
Text files containing DNS resource records that define the configuration details of a domain zone. Domain registries publish daily zone files detailing all active domain name delegations under a TLD, which serves as the primary data discovery feed for newly registered domain lists.
Domain Entities
Registrant
The individual or corporate entity that holds the rights to use a domain name. This is the domain 'owner' listed in the WHOIS contact blocks.
Registrar
An accredited organization (like GoDaddy, Namecheap, or Cloudflare) authorized to sell domain registrations to the public and write database records directly to the registry.
Registry
The master database operator responsible for managing all domain registrations under a specific Top-Level Domain (TLD). For example, Verisign is the registry operator for Verisign's .com and .net extensions.
IANA ID (Internet Assigned Numbers Authority ID)
A unique numeric identifier assigned to ICANN-accredited registrars. Using IANA IDs allows database systems to track registrars independently of name spelling changes.
Registrar Lock
A security status code (ClientTransferProhibited) set by a registrar that prevents a domain name from being unauthorizedly transferred to a different registrar. This flag must be removed before any domain acquisition.
WHOIS Parser
A software utility designed to translate raw, unstructured, text-based WHOIS record blocks into normalized, structured data formats like JSON or SQL. Standardizing WHOIS inputs is complex due to the hundreds of varying registrar formats.
Privacy & Compliance
GDPR Redaction
The masking of personal contact details (names, emails, phones) in public WHOIS outputs to comply with the European Union's General Data Protection Regulation. Redacted fields are usually replaced with terms like 'Redacted for Privacy'.
Privacy / Proxy Shield
A commercial service offered by registrars (e.g. WhoisGuard, Domains By Proxy) that replaces the registrant's private contact details with secondary forwarding details to prevent spam harvesting.
Redacted for Privacy
The placeholder text inserted by domain registrars in WHOIS records to replace personal registrant details (such as names, addresses, and emails) when compliance with privacy laws like GDPR is required.
WhoisGuard
A generic term representing commercial registration privacy services that swap public contact details with proxy forwarding addresses to protect domain owners from email spam harvesting.
Technical Settings
Nameservers (DNS)
The servers that point a domain name to specific web servers or mail servers. Valid WHOIS records always list the active nameservers associated with a registered domain.
Domain Lifecycle Dates
The three critical timestamps inside a WHOIS database record: Creation Date (when the domain was registered), Update Date (when it was last modified), and Expiration Date (when it will return to the open market if unpaid).
Redemption Period
A domain lifecycle grace period (typically 30 days) that occurs after a domain name expires and is deleted. During this period, the original registrant can retrieve the domain back by paying a restoration fee before it is released to the general public.
MX Record (Mail Exchanger)
A resource record in the DNS that specifies the mail server responsible for accepting email messages on behalf of a domain name. WHOIS analysis often correlates registrant contacts with MX record configurations.
DNSSEC (Domain Name System Security Extensions)
A suite of extension specifications for securing DNS data by signing records cryptographically, protecting clients from forged DNS data and spoofing attacks.
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