TLD registry lookup: who runs each domain extension, and does it have RDAP?
In short: Paste extensions, domains or URLs and see, for each top-level domain, its sponsoring organisation and technical contact's organisation from IANA's root zone records, when it entered the root, whether it's DNSSEC-signed, and whether its registry offers RDAP for domain lookups. Limit: IANA's records name the sponsor and contacts; they don't include prices, eligibility rules or registrar lists.
A TLD registry lookup reads IANA's root zone record for a domain extension. Paste extensions, domains or URLs, up to 100 (500 after a Google sign-in): each TLD shows its sponsoring organisation, technical contact's organisation, type, the year it entered the root, DNSSEC and its RDAP server, marked Has RDAP, No RDAP, Not a TLD or Lookup failed.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. See pricing
Sample result
.io is a country-code TLD with no RDAP service, so its domains need WHOIS for lookups.
- Extension
- .io
- Type
- Country code
- DNSSEC
- Signed
What this means for you
Know who runs each extension, whether it's DNSSEC-signed, and where domain lookups under it go.
- Sponsor and technical contact's org
- Year it entered the root
- DNSSEC and RDAP server
- 100 extensions a run, 500 signed in
- TLD
- Registry
- RDAP
By SimpleVerifier Team · Last updated
Have a list of domains, not just extensions?
- Paste the domains here as they are; each is reduced to its extension and repeats are merged.
- Look up the domains themselves with the bulk WHOIS lookup, which uses RDAP where these results show one.
- Emailing addresses on these domains? Check the list at /verify. The first 100 email checks are free with a Google sign-in, no card.
How do I find out who runs a domain extension?
- Paste extensions (.io), domains (acme.co.uk) or URLs, one per line: up to 100 a run, or 500 after a free Google sign-in. Each line is reduced to its last label, and repeats are merged.
- Press Look up registries. Each TLD is looked up once in IANA's root zone RDAP service.
- Read the sponsor, technical contact's organisation, DNSSEC status and where domain lookups under the TLD go.
- Download the CSV with one row per extension.
Example
- You enter
- Four lines:
.io,.xyz,acme.co.ukand.notreal. - You get
.ioNo RDAP: a country-code TLD, DNSSEC-signed, with no RDAP service in IANA's bootstrap, so domain lookups need WHOIS..xyzHas RDAP: a generic TLD whose sponsor and technical contact are different companies..uk(from acme.co.uk) Has RDAP at Nominet's server..notrealNot a TLD. Download the CSV.- Limits
- Up to 100 extensions a run without an account and 500 when signed in with Google. One IANA request per extension.
Who runs a top-level domain?
Every TLD in the root zone has a manager on record at IANA, shown in the Root Zone Database: the sponsoring organisation, plus administrative and technical contacts. For a generic TLD like .xyz the sponsor is the company that holds the registry agreement with ICANN; for a country code like .io or .uk it's the organisation the country or territory designated. The technical contact's organisation is often a back-end operator that runs the registry systems for the sponsor, which is why .xyz shows one company as sponsor and another as technical contact.
The lookup reads these records from IANA's RDAP service, rdap.iana.org, which answers in the JSON format of RFC 9083. Only organisation names are shown; contact people and addresses are left out.
Why does it matter whether a TLD has RDAP?
RDAP is the structured replacement for WHOIS. Which registry answers RDAP for which TLD is published in IANA's bootstrap file (RFC 9224), and ICANN made RDAP the definitive source for generic TLD registration data from 28 January 2025, so every gTLD has one. Country codes set their own rules: on the day this page was written, .io, .de, .jp, .cn and .us were among those with no RDAP service in the bootstrap file.
That decides what a domain lookup can tell you. Under a TLD with RDAP, a WHOIS lookup or domain age check can read the registration date and registrar directly from the registry. Under one without, those facts need the registry's own WHOIS server or website, and a bulk tool can only report that it couldn't tell.
Who uses this tool, and for what?
- Domain investors
- See who runs an extension and whether it's DNSSEC-signed before buying names under it.
- Cold email teams
- Check the registry behind a new sending-domain extension.
- Security analysts
- Map which registries sit behind the TLDs in a list of suspicious domains.
- Developers
- Find which TLDs in a dataset can be queried with RDAP, and where.
What can’t this tool tell you?
- IANA's records name the sponsor and contacts; they don't include prices, eligibility rules or registrar lists.
- The technical contact's organisation is often, but not always, the back-end registry operator.
- Second-level endings like co.uk are read as their TLD, .uk.
- Up to 100 extensions a run without an account and 500 signed in.
Common questions
- What do I get for acme.co.uk?
- The facts for .uk, the top-level domain. Second-level endings like co.uk are run by the same registry (Nominet for .uk) but aren't separate entries in the root zone.
- What is the difference between a gTLD and a ccTLD?
- Country-code TLDs are two letters (.uk, .io, .ai) and follow the policies of the country or territory's chosen manager. Generic TLDs (.com, .xyz, .app) run under contracts with ICANN. Internationalised TLDs (.рф) are shown in Unicode and their xn-- form.
- Does it work for internationalised extensions?
- Yes. Paste .рф or xn--p1ai; both are looked up as xn--p1ai and shown in both forms.
- Does it show prices or registration rules?
- No. Those aren't in IANA's records. The registry's own site, linked under each result when IANA lists one, has its policies.
- Can I look up many extensions at once?
- Yes. 100 extensions a run without an account and 500 after a free Google sign-in, with a CSV. Repeated extensions count once.
- Is the TLD registry lookup free?
- Yes, it's a free tool with no card. One request to IANA per extension, cached for a day.
Sources
You audited one domain. Cold outreach means thousands.
This tool checks a domain you type in. It will not tell you which addresses at that domain are real.
- Bulk mailbox verification with real SMTP checks
- The email finder — name plus company to a verified address
- Website enrichment for emails, owner names and socials
Plans from $9 a month, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.