Glossary

Second-level domain (SLD)

The second-level domain is the part directly left of the TLD — "example" in example.com. Some registries also create second-level spaces such as .co.uk or .com.au, which is why those look like TLDs but aren't.

In example.co.uk the TLD is .uk; "co" is a second-level space Nominet created for companies, and "example" sits at the third level. Countries like the UK, Australia, Brazil and Japan used these category spaces for years before (or instead of) selling names directly under the TLD.

Examples

Quick answers

Is .co.uk a TLD?

No. The TLD is .uk; .co.uk is a second-level space under it.