I'm looking for a reliable list of country-code top-level domains (ccTLDs) where registrations must use an additional level such as .co.uk or .com.br instead of being made directly under the country code. I found a table that lists second-level domains, but I'm not sure whether that accurately describes registration requirements or something else. Is there a better source for this information?
3 Answers
It depends on what you mean by “require.” Some registries use structures like example.co.uk, while also allowing direct registrations such as example.uk. Brazil has several categorized options, including .com.br and .edu.br, but direct registrations under .br may also be available in some cases. A list of second-level domains can help, but it doesn’t necessarily show which levels are mandatory.
For authoritative registration requirements, check each ccTLD registry’s own policy documentation. IANA’s root zone database identifies the operator responsible for each ccTLD, and that operator publishes the eligibility and naming rules. This is more reliable than a static table because policies can change, as happened with domains such as .uk, .nz, and .au.
The Public Suffix List is useful for understanding where the registrable portion of a domain ends. Browsers use it for things like cookie boundaries, and it includes patterns such as .co.uk and hosted subdomain services. However, it describes suffix and cookie-scope boundaries—not necessarily whether a registry requires a second-level domain for registration.
That distinction is important: both .uk and .co.uk can appear in the list even though registrations are possible at more than one level. The list marks domain boundaries rather than enforcing registry rules.