WHOIS: How to Check Domain Information

What Is WHOIS

WHOIS (from the English "who is") is a protocol and corresponding database that stores registration information about domain names, IP addresses, and autonomous systems. When someone registers a domain name, their contact information and technical registration details are entered into the WHOIS database, which is available for public viewing.

The WHOIS protocol has existed since 1982 and was created to ensure transparency of internet resources. Today it remains the primary tool for checking domain information, although its operation has changed significantly with the introduction of GDPR and other personal data protection laws.

Historically, WHOIS was developed by Elizabeth Feinler at Stanford Research Institute to identify users of the ARPANET network — the predecessor of the modern internet. Since then, the protocol has come a long way, but its basic principle remains unchanged: to provide access to registration information for network resources.

What Information Can You Find Through WHOIS

A standard WHOIS query for a domain name returns the following information:

• Registrant: the domain owner — name, organization, address, email, phone number
• Registrar: the company through which the domain was registered (e.g., GoDaddy, Namecheap, Cloudflare)
• Dates: registration date, last update date, registration expiration date
• Nameservers: DNS servers that serve the domain and handle name resolution
• Domain status: active, locked, pending delete, and other status codes according to the EPP standard
• Administrative contact: the person responsible for domain management at the organizational level
• Technical contact: the person responsible for DNS technical support and server infrastructure

Try checking information about any domain using our WHOIS Lookup tool — results are displayed instantly in a convenient format that is understandable even for users without technical experience.

How the WHOIS Protocol Works

WHOIS Server Hierarchy

WHOIS operates on a hierarchical model. When you make a query, it first reaches a root WHOIS server (for example, whois.iana.org), which redirects you to the WHOIS server for the appropriate domain zone. For .com, this is whois.verisign-grs.com, for .org it is whois.pir.org, and for .io it is whois.nic.io.

The domain zone server may in turn redirect the query to the WHOIS server of the specific registrar for more detailed information. This hierarchy ensures distributed data storage and reduces the load on individual servers, allowing the system to process millions of queries daily.

Port and Protocol

WHOIS operates on port 43 via TCP connection. The client sends a text query (domain name or IP address), and the server responds with a text block of information. The protocol is maximally simple — there is no authentication, encryption, or complex query structure, which makes it both accessible and vulnerable to abuse.

Due to the lack of encryption, WHOIS queries can be intercepted by third parties, creating additional privacy risks. This is exactly why modern alternatives like RDAP use HTTPS to protect communication between client and server.

RDAP — The Successor to WHOIS

RDAP (Registration Data Access Protocol) is a modern replacement for WHOIS developed by the IETF. Unlike WHOIS, RDAP returns data in structured JSON format, supports HTTPS encryption, and has a standardized authorization system. ICANN has required gTLD registrars to support RDAP since 2019, but the complete transition is not yet finished, and classic WHOIS remains widely used across the internet.

WHOIS Privacy: Protecting Personal Data

The Problem with Open Data

Traditionally, WHOIS published the full contact information of domain owners: name, address, phone number, and email. This created serious problems — spam to the registrant's email, unwanted calls from hosting and SEO service sellers, and sometimes even physical threats. Malicious actors used WHOIS data for social engineering and targeted phishing attacks, forging letters on behalf of the registrar.

Impact of GDPR

After the General Data Protection Regulation (GDPR) took effect in 2018, domain registrars began hiding personal data from WHOIS. Now, instead of the owner's name and address, you often see "REDACTED FOR PRIVACY" or the registrar's proxy service data. This significantly improved privacy but complicated legitimate uses of WHOIS, such as fighting cybercrime and protecting intellectual property.

GDPR affected not only European domains — most global registrars applied a unified data hiding policy for all clients regardless of their location, in order to avoid legal risks and simplify operational processes.

WHOIS Privacy Protection (Proxy/Privacy Service)

Even before GDPR, WHOIS privacy services existed that replaced the owner's contact details with those of a proxy company. Most registrars offer this service for free or for a small fee. When using WHOIS Privacy, your real contact information remains with the registrar but is not published in the public WHOIS database. In the event of legal claims, the registrar can disclose your data by court order.

Practical WHOIS Use Cases

1. Checking Domain Ownership

If you want to buy a domain or contact its owner, WHOIS is the first step. Even if data is hidden behind Privacy Protection, you can usually find an email form for contact through the registrar or proxy service. This is especially useful when the domain you need is already taken but is not being actively used by its owner.

2. Checking Registration Expiration

WHOIS shows the domain registration expiration date. This is useful for monitoring domains you are interested in — you can register a domain as soon as it becomes available after expiration. It also helps verify that your own domain does not need renewal. Specialized services (drop-catching) exist that automatically attempt to register a domain the moment it becomes available.

3. Identifying Phishing Sites

If a site looks suspicious, a WHOIS check can reveal important information. Phishing sites typically have a recent registration date (a few days or weeks old), use cheap or free registrars, and have hidden ownership data. A legitimate internet bank registered three days ago is an obvious red flag that should raise serious concerns.

4. Legal Purposes

Law enforcement and lawyers use WHOIS to identify owners of websites that violate copyright laws, trademarks, or engage in fraudulent activities. WHOIS data can serve as evidence in legal proceedings and grounds for filing a complaint under the UDRP (Uniform Domain-Name Dispute-Resolution Policy) procedure to challenge domain names that infringe on trademarks.

5. Competitor Analysis

SEO specialists and marketers use WHOIS to analyze competitor domains: when they were registered, which registrar is used, which DNS servers are configured (which may indicate the hosting provider). Domain age is one of the ranking factors in search engines — older domains typically have higher authority in the eyes of Google.

6. Security Research

Cybersecurity specialists use WHOIS to analyze the infrastructure of malicious actors. Checking nameservers, registrars, and dates helps identify networks of interconnected malicious domains. If dozens of domains are registered to a single registrant from the same IP block, this may indicate a coordinated malware distribution campaign.

Domain Statuses in WHOIS

WHOIS displays statuses defined by the EPP (Extensible Provisioning Protocol) standard. The main ones include:

• clientTransferProhibited: the domain is protected from unauthorized transfer to another registrar — recommended for all important domains
• clientDeleteProhibited: the domain is protected from accidental deletion — an additional layer of security
• serverHold: the domain has been blocked by the registry — DNS is not served, and the site is inaccessible
• redemptionPeriod: the domain has been deleted but can still be restored within 30 days for an additional fee
• pendingDelete: the domain is awaiting final deletion and will soon be available for registration by anyone
• active/ok: the domain is functioning normally without any restrictions or blocks

Understanding statuses helps diagnose domain problems. If your website suddenly stops working, checking the status through WHOIS may reveal that the registry has blocked the domain due to non-payment or policy violation.

Limitations and Issues with WHOIS

Rate Limiting

WHOIS servers limit the number of queries from a single IP address to protect against abuse and mass data harvesting. If you make too many requests in a short period, your IP may be temporarily blocked for several hours or even days. Our WHOIS Lookup tool is optimized for fast and reliable queries without the risk of being blocked or throttled.

Unstructured Data

Different registrars and domain zones return WHOIS data in different formats. There is no single formatting standard, which complicates automatic parsing. RDAP partially solves this problem through its JSON format, but it does not yet cover all domain zones, especially ccTLDs (country code top-level domains).

Incomplete Information

Due to GDPR and WHOIS Privacy, a significant portion of useful information is now hidden. This complicates security research and the fight against cybercrime, although it simultaneously protects the privacy rights of ordinary users and domain owners. The balance between transparency and privacy remains one of the most challenging issues in internet resource management.

Domain Zones and WHOIS Specifics

Different domain zones have different WHOIS rules. Generic TLDs (.com, .org, .net) are regulated by ICANN and follow unified standards. Country code TLDs (.ua, .de, .uk) are regulated by national organizations and may have their own rules for data display. For example, the .de zone (Germany) traditionally shows minimal information, while .com provides maximally detailed data according to ICANN policy.

Conclusion

WHOIS remains an indispensable tool for checking domain information, despite privacy-related limitations. Whether you need to verify domain ownership, check a registration expiration date, or analyze a suspicious website, WHOIS provides valuable information in seconds. Use our free WHOIS Lookup tool to get detailed information about any domain in the world instantly.