The complete domain lookup guide

What is a domain lookup?

Domain lookup refers to any query used to retrieve a domain's registration data. After you buy a domain from a registrar, the registrar records data such as the registrar, creation and expiry dates, nameservers, DNSSEC and domain status in the TLD registry's database; a domain lookup is essentially reading that data back in real time from the authoritative registry or registrar servers. In practice it works on three layers:

• Registration layer: whether a domain is registered, who the registrar is, and when it expires — the most common WHOIS/RDAP lookup.
• Resolution layer: which IPs, mail servers (MX) and TXT records a domain points to — a DNS lookup.
• History layer: which nameservers a domain used in the past and whether it changed registrars — change tracking.

This site integrates the three protocols WHOIS, RDAP and DNS, so entering a single domain returns the complete result at once.

Why do you need a domain lookup?

Domain lookup has a very wide range of use cases and is part of the daily workflow for enterprise IT, security researchers, domain investors and marketers alike:

• Check availability before registering: confirm whether the domain you want is taken; if it is, check the expiry date to estimate when it might be released.
• Acquiring a domain: verify the registrar, the registrant class, and whether it is transfer-locked (clientTransferProhibited).
• Troubleshooting a website: confirm the nameservers correctly point to your DNS provider.
• Investigating suspicious domains: spotting anomalies in the registration data and creation time is a common technique in anti-fraud and security research.
• Routine audits: check expiry dates regularly to avoid a domain lapsing and being drop-caught by someone else.

What protocols does domain lookup use? WHOIS, RDAP and DNS

Domain lookup looks like one action, but three protocols work behind it, each with its own role — WHOIS/RDAP belong to the registration-management layer, DNS to the resolution layer:

• WHOIS: a plain-text protocol defined in RFC 812 (1982), with RFC 3912 (2004) as the current version, connecting over TCP port 43 to registry/registrar servers and returning human-readable text.
• RDAP (Registration Data Access Protocol): the WHOIS successor defined by the IETF in RFC 7480–7484 (2015), using HTTPS and JSON and consistent across TLDs; every ICANN gTLD is required to serve it, and most major ccTLDs support it too.
• DNS: queries the resolution layer — which IPs, mail servers (MX) and TXT records a domain points to.

This site automatically determines which protocols a TLD supports, prefers RDAP and falls back to WHOIS when necessary, and adds DNS results — completing all three lookups at once.

How to choose a domain lookup tool?

The domain lookup tools on the market broadly fall into three categories, each with trade-offs:

• Command-line tools (Unix whois/dig): fast, but they require technical background, and for non-RDAP TLDs you must specify the upstream server manually.
• Web tools (whois.net.tw, whois.com, who.is): enter a domain and get a structured result — ideal for general users.
• API services: offer a RESTful interface and batch lookups, suited to automation workflows and code integration.

When choosing, consider: whether it supports WHOIS/RDAP/DNS together, whether it connects directly to authoritative servers (avoiding stale caches), whether it covers every common TLD (.com, .net, .tw, .jp, .io, etc.), whether it is completely free with no signup, and whether the output is easy to read. This site offers all of the above and provides a Traditional Chinese interface, making it especially suited to users in Taiwan and the Chinese-speaking world.

What legal and privacy issues affect domain lookup?

Since ICANN's 2018 post-GDPR policy, the personally identifying data in domain lookup results (registrant name, email, phone) is mostly masked by the registrar as "REDACTED FOR PRIVACY":

• Domains registered by natural persons usually have their personal data masked; domains registered by companies or organizations mostly still disclose the organization's information.
• If you need the full data for law enforcement or security research, you can request differentiated access (Tiered Access) from the registrar under ICANN's rules, limited to trusted bodies such as law enforcement and CSIRTs.
• Domain lookup itself is legal and public, but using the results for spam, harassment or attacks violates data-protection and computer-crime laws.

This site caches lookup results only briefly and never sells or forwards any query data.

How to look up domain registration information

1. 1

   Enter the domain name or IP address

   Type the domain name (e.g. example.com) or IP address into the search box on the homepage and press Lookup.

2. 2

   Retrieve real-time WHOIS results

   The tool connects directly to the authoritative WHOIS or RDAP server for the domain's TLD and returns the latest registration data, usually within a few seconds.

3. 3

   Read the domain registration details

   Review the registrar name, creation date, expiry date, nameservers, and domain status to confirm ownership and validity.

Run a domain lookup now

Head to the home page, type any domain, and see the full domain lookup result.

References

• RFC 3912 — WHOIS Protocol Specification — WHOIS protocol
• RFC 7480–7484 — Registration Data Access Protocol (RDAP) — RDAP standard
• ICANN — Registration Data / RDAP — gTLD registration data policy
• IANA — RDAP Bootstrap Service Registry — RDAP endpoints for each TLD
• ICANN — EPP Status Codes — Domain status code reference