Anatomy of a domain name?

Domain names are typically broken up into two or three parts, each separated by a dot. When read right-to-left, the identifiers in domain names go from most general to most specific. The section to the right of the last dot in a domain name is the top-level domain (TLD). These include the ‘generic’ TLDs such as ‘.com’, ‘.net’, and ‘.org’, as well as country-specific TLDs like ‘.uk’ and ‘.jp’.

To the left of the TLD is the second-level domain (2LD) and if there is anything to the left of the 2LD, it is called the third-level domain (3LD). Let’s look at a couple of examples:

For Google’s US domain name, ‘google.com’:

  • ’.com’ is the TLD (most general)
  • ’google’ is the 2LD (most specific)

But for Google UK’s domain name, ‘google.co.uk’:

  • ’.com’ is the TLD (most general)
  • ’.co’* is the 2LD
  • ’google’ is the 3LD (most specific)

*In this case the 2LD indicates the type of organization that registered the domain (.co in the UK is for sites registered by companies)