As of current knowledge and available resources, there is no Top-Level Domain (TLD) with the extension “.locker”. Top-Level Domains (TLDs) are the last segment of a domain name, usually the extension that follows right after the last dot in a web address. Existing TLDs are typically classified into three types: country-code TLDs (ccTLDs like .us, .uk, .de), generic TLDs (gTLDs like .com, .net, .edu), and infrastructure TLD (.arpa). These are maintained by the Internet Assigned Numbers Authority (IANA) which is a department of ICANN (Internet Corporation for Assigned Names and Numbers) (The Linux Professional Institute, The Great DNS Quiz, LPI Linux Certification in a Nutshell, 3rd ed., 2009).
Further specific TLDs are also maintained, for example, the sponsored TLDs (sTLDs) which are specialized and represent specific communities. Introduced in 2001/2002, examples of sTLDs include .aero for the air-transport industry, .coop for cooperatives, or .museum for museums (Museum Domain Management Association, About .museum, MDMA FAQ, 2016).
In recent years (starting from 2012), ICANN started to expand the domain name system and introduce many new gTLDs, a program called New gTLD program. Hundreds of new TLDs are now operating in the root zone which is the highest level of the domain system structure of the Internet. New TLDs like “.fishing”, “.restaurant” or “.sport” have been established and operational. However, as already mentioned, the “.locker” extension is not one of these TLDs. You can always check this yourself using the root zone database IANA maintains which contains the authoritative record of all TLDs (Internet Assigned Numbers Authority, Root Zone Database, IANA website, constantly updated).
In conclusion, “.locker” is not currently in use or recognized as a TLD in the domain name system of the Internet according to available official resources. The TLD landscape however is dynamic and can change, as ICANN sometimes introduces new TLDs based on a predetermined process and criteria (ICANN, New gTLD Program, ICANN website, 2016). Newly registered TLDs are considered upon specified times along with specific terms and conditions usually involving a hefty monetary sum and various other requirements to ensure that the TLD can be managed and operated smoothly.
