WHOIS·RDAP 조회

(문서는 영어)

What it does

This tool looks up registration data for a domain name, an IP address, or an

Autonomous System NumberAutonomous System NumberA number identifying one routing domain on the internet (one AS = one network under a single policy), used by BGP to exchange routes.Learn more

(ASN) — the kind of information historically associated with “WHOIS”: registrar, registration and expiry dates, status flags,

nameserversnameserversA DNS server that answers queries for a zone, telling the world where a domain's records (and its mail and web) live.Learn more

, and the

DNSSECDNSSECA DNS extension that cryptographically signs zone records, letting resolvers verify answers were not forged or altered in transit.Learn more

signing state.

It does this with

RDAPRDAPThe modern JSON REST protocol for WHOIS-style registration data (domains, nameservers, entities), replacing the legacy plain-text WHOIS protocol.Learn more

(

Registration Data Access ProtocolRegistration Data Access ProtocolThe modern JSON REST protocol for WHOIS-style registration data (domains, nameservers, entities), replacing the legacy plain-text WHOIS protocol.Learn more

), the modern HTTPS/JSON successor to the legacy port-43 WHOIS protocol. Your browser fetches the answer directly from the authoritative registry over HTTPS. For the ~1% of registries that block browser access (no CORS header), the tool retries once through a strictly allowlisted CosmoDev relay — those results carry a visible via relay badge; every other lookup stays browser-direct, with CosmoDev keeping no record of what you search.

RDAPRDAPThe modern JSON REST protocol for WHOIS-style registration data (domains, nameservers, entities), replacing the legacy plain-text WHOIS protocol.Learn more

returns structured JSON, so the result is clean fields rather than the unstructured text wall legacy WHOIS produces. ICANN has required RDAP for all generic TLDs (.com, .org, .dev, …) since 2019, so coverage for domains you actually look up is essentially complete.

How to use it

1. Type a domain (example.com), an IPv4 or IPv6 address (192.0.2.1, 2001:db8::1), or an

   ASNASNA number identifying one routing domain on the internet (one AS = one network under a single policy), used by BGP to exchange routes.Learn more

   (AS15169) into the big lookup box under “Look up a domain”. You can also paste a full URL; the scheme, path, and port are stripped automatically. As you type, a chip under the input shows what was detected (Domain, IPv4 address, IPv6 address, or

   ASNASNA number identifying one routing domain on the internet (one AS = one network under a single policy), used by BGP to exchange routes.Learn more

   ), or a subtle “Not recognized” hint when the text matches none of them.
2. Press Lookup (or Enter). The example chips (example.com, 192.0.2.1, AS15169) fill the input and run the lookup in one tap. Clear resets everything; it appears only once there is something to clear.
3. Read the result. The header card shows the name, the detected kind, the registry handle, and the

   DNSSECDNSSECA DNS extension that cryptographically signs zone records, letting resolvers verify answers were not forged or altered in transit.Learn more

   state. Below it: the EPP status flags, with an expandable plain-language legend for the common ones; then two columns on wide screens. The left column holds the sandboxed Preview and a timeline of the registered → last changed → expires dates, with a relative hint next to the expiry date (“in 240 days”) that turns into a warning when expiry is less than 30 days away. The right column holds the registrar (with abuse contact) and the

   nameserversnameserversA DNS server that answers queries for a zone, telling the world where a domain's records (and its mail and web) live.Learn more

   , with a count badge. On narrow screens the cards stack in that order.
4. For domain lookups, the Preview card in the left column loads the live site in a locked-down iframe. Many sites refuse embedding (X-Frame-Options), so a blank preview is normal and expected; use the Visit site link in the card corner, or the Visit site button in the tool header, to open the site in a new tab.
5. Use the Share button in the tool header to copy a link that encodes your query in the URL (?q=…), so the same lookup runs when the link is opened.

Examples

A registered domain — cloudflare.com returns registrar (Cloudflare, Inc.), the registration/expiry dates, status flags like clientTransferProhibited, the

nameserversnameserversA DNS server that answers queries for a zone, telling the world where a domain's records (and its mail and web) live.Learn more

, and the

DNSSECDNSSECA DNS extension that cryptographically signs zone records, letting resolvers verify answers were not forged or altered in transit.Learn more

signing state.

An IP address — 1.1.1.1 resolves through the regional internet registry (RIPE/APNIC/ARIN/…)

RDAPRDAPThe modern JSON REST protocol for WHOIS-style registration data (domains, nameservers, entities), replacing the legacy plain-text WHOIS protocol.Learn more

service and returns the network range, holder, and country.

An

ASNASNA number identifying one routing domain on the internet (one AS = one network under a single policy), used by BGP to exchange routes.Learn more

— AS13335 returns the AS name (Cloudflare), the holder, and the registered route ranges.

A

TLDTLDThe last label of a domain name (.com, .org, .dev). Registries operate each TLD and set its registration rules.Learn more

the browser cannot read — some registries serve

RDAPRDAPThe modern JSON REST protocol for WHOIS-style registration data (domains, nameservers, entities), replacing the legacy plain-text WHOIS protocol.Learn more

but send no CORS header, so a browser is not allowed to read the response. The tool retries those once through its allowlisted relay and shows the result with a via relay badge; only when the relay also fails does it explain the block instead of failing silently.

Good to know

• Private by architecture: browser-direct lookups go from your browser straight to the registry — CosmoDev’s servers are not in the path and store nothing. Relayed lookups (badged via relay) transit our Worker because that registry blocks browser access; the relay validates every target against the IANA bootstrap before fetching and keeps no record either.
• The registry always sees your query: to answer a question about a domain, the domain name must be sent to the authoritative server. That is inherent to the protocol, not a choice this tool makes.
• ~99% of TLDs work browser-direct. A full sweep of the IANA bootstrap found 99.1% of responding registries send the CORS header a browser needs. The rest fall back to the allowlisted relay automatically; only ccTLDs absent from the bootstrap entirely (like .de) cannot be relayed and show a clear explanation instead of a broken result.
• HTTPS, not plaintext: unlike legacy WHOIS on port 43,

  RDAPRDAPThe modern JSON REST protocol for WHOIS-style registration data (domains, nameservers, entities), replacing the legacy plain-text WHOIS protocol.Learn more

  runs over TLS, so your query is encrypted in transit.
• This is the first CosmoDev tool that makes outbound network requests. Every other tool runs purely inside your browser; this one talks to external registries to fetch live data.
• Learn more: WHOIS to RDAP — why

  RDAPRDAPThe modern JSON REST protocol for WHOIS-style registration data (domains, nameservers, entities), replacing the legacy plain-text WHOIS protocol.Learn more

  replaced WHOIS, and how browser-direct lookup works.