What is an SLD?¶

A Second Level Domain (SLD) is the part of the address that comes directly before the Top Level Domain (TLD), and usually provides more information on the organisation that registered the domain.

In many cases the SLD is the middle bit of a domain that goes between www. and the domain name extension (for example, .com, .org) at the end of the address. For example, in <www.ukfast.co.uk>, ukfast is the SLD.

However, it can also come after the dot to tell you more about the type of entity the domain belongs to. For example, in the .uk namespace, a university or other academic institution would register under .ac.uk, instead of .co.uk, as it signposts that the organisation is a learning institution. In this case, .ac is the SLD.