SecondLevel

Secondlevel, in the context of domain naming, refers to the second-level domain (SLD) within the Domain Name System (DNS). In a domain such as example.com, the portion "example" is the second-level domain, which sits directly to the left of the top-level domain (TLD) "com." The SLD is typically the registrable part of the domain that identifies the organization or purpose for the domain name.

In the DNS hierarchy, the TLD is the highest level shown in the domain name, with the SLD beneath it. Registrations of second-level domains are managed by registries and registrars authorized for each TLD. Most major TLDs, like .com, .net, and .org, allow individuals or organizations to register any eligible SLD directly under the TLD. Other TLDs, such as many country-code TLDs, structure registrations through predefined second-level labels like co, ac, or edu under the country code (for example, example.co.uk or example.ac.uk), before a registrant can register an overall domain name.

The term secondlevel can also intersect with broader terminology. For example, the registrable domain (often referred to as eTLD+1) includes the TLD plus its associated SLDs, and is the portion typically used to identify a website or service in practice. Subdomains, such as www or blog, are created under the SLD to organize resources. The exact rules and available SLDs vary by registry and TLD.