What is a domain name?

A domain name is a string that represents a realm of administrative autonomy, authority, or control on the Internet. It's often used to identify services like websites and email services. Domain names are part of the Domain Name System (DNS), and any name registered in the DNS is a domain name.

Domain names are used to identify various Internet resources, such as computers and services, with a memorable text label instead of numerical IP addresses. A single domain name can represent multiple resources or a single instance. In the context of individual Internet host computers, domain names function as identifiers, also known as hostnames. These hostnames are often utilized in Uniform Resource Locators (URLs) to access Internet resources, such as websites (e.g., premiumflying.com).

Domain names serve as straightforward labels for identifying and accessing resources online. They play a crucial role in systems like SIP, Domain Keys in email, and other URI formats. A key role of domain names is to provide memorable and recognizable names for numerically addressed resources, enabling seamless relocation of resources within network address hierarchies. This often involves changing the IP address and its translation to and from the domain name. Companies can select a domain name that reflects their own name, making it easier for Internet users to locate them.

A general domain name represents a broad category, such as an industry, instead of a specific entity, like a company name, for instance, sswbc.com, fingerpay.me, or simplepay.info. These generic names can be the basis for brand creation and can hold value. Domain names are commonly just called domains, and those who register them are often referred to as domain owners. However, registration doesn't grant legal ownership, only exclusive use for a specific period. Using domain names in business could make them subject to trademark law.

The initial commercial Internet domain name, located in the com TLD, was registered as symbolics.com on March 15, 1985, by Symbolics Inc., a Massachusetts-based computer systems company. By 1992, the number of registered com domains was under 15,000. By the first quarter of 2015, this number had surged to 294 million. As of December 21, 2014, the com TLD housed 115.6 million domains, including 11.9 million business and e-commerce sites, 4.3 million entertainment sites, 3.1 million finance-related sites, and 1.8 million sports sites. By July 15, 2012, the com TLD had more registrations than all ccTLDs combined. As of December 31, 2023, the total number of registered domains was 359.8 million.

Currently, the Internet Corporation for Assigned Names and Numbers (ICANN) is responsible for overseeing the top-level design and infrastructure of the Internet's domain name system. ICANN grants authorization to domain name registrars, allowing them to register and reassign domain names.

The domain name system is structured as a tree of domain names, with each node containing relevant information. This tree branches into zones, starting from the root zone of the Domain Name System.

The domain name system, established in the 1980s, categorized domains into two major groups. The country-code top-level domains (ccTLD) typically derived their names from the two-letter ISO-3166 country codes. Additionally, a set of seven generic top-level domains (gTLD) were introduced, encompassing various name categories and multi-organizations. These gTLDs include gov, edu, com, mil, org, net, and int. These top-level domains (TLDs) constitute the highest level of Internet domain names and form the root zone of the hierarchical Domain Name System. Every domain name concludes with a TLD identifier.

As the Internet expanded, there was a need for more generic top-level domains. By October 2009, there were 21 generic and 250 two-letter country-code top-level domains. The ARPA domain also serves specific functions within the Domain Name System. In 2008, during the 32nd ICANN Meeting in Paris, a new TLD naming policy was initiated to facilitate the introduction of new generic top-level domains. This change was expected to lead to the registration of hundreds of new top-level domains. The program began in 2012 and received 1930 applications, leading to the milestone of 1000 live gTLDs by 2016.

The Internet Assigned Numbers Authority (IANA) is responsible for keeping an annotated directory of top-level domains, which is part of the Domain Name System's root zone database.

Second-level domains, such as .com or .net in paypage.co.uk, are followed by third-level domains and so on, creating a domain name hierarchy. These labels, separated by dots, indicate subdomains that are subordinate to their parent domain. For instance, 'service' in service.tx.simplepay.us is a sub-domain of 'tx.simplepay.us'. Deep levels of subdomain ordering are seen in IPv6 reverse resolution DNS zones.

Domain name use is granted through domain name registrars, accredited by the Internet Corporation for Assigned Names and Numbers (ICANN). ICANN governs the Internet's naming system. Each top-level domain (TLD) is managed by an administrative organization, known as a registry. This organization maintains the TLD's name database and receives registration data from registrars. This information is then released through the WHOIS protocol, a specific service.

Domain name registrars and registries typically bill an annual fee for granting users domain name delegation and supplying initial name servers. This transaction is commonly referred to as a domain name sale or lease, but it doesn't establish any legal ownership. The correct terms for individuals with domain use rights are "registrants" or "domain holders".

ICANN keeps a record of all top-level domain registries and domain name registrars. The details of a domain, such as the registrant, name servers, and expiration dates, can be accessed using the WHOIS protocol. Generally, for around 250 country-code top-level domains (ccTLDs), the domain registries are responsible for managing the WHOIS (including registrant, name servers, expiration dates, etc.) information.

Domain name registries, also known as network information centers (NIC), sometimes act as registrars for end-users. The primary registries for generic top-level domains, such as .com, .net, .org, .info, and others, typically operate under a registry-registrar model. This model involves numerous domain name registrars, as listed by ICANN[24] or VeriSign[25]. In this system, the registry is only responsible for managing the domain name database and maintaining relationships with registrars. Registrants, or domain name users, are clients of the registrar, who may sometimes be part of a reseller chain.

Several other DNS root providers exist, seeking to either challenge or enhance ICANN's domain name management. Yet, many of these alternatives have not gained extensive acceptance. Consequently, domain names from these less-known roots often require specific settings to function on most internet-connected devices.

When registering a domain name and controlling the newly established domain area, registrars utilize various crucial domain-related details.

A domain name is made up of one or more components, known as labels, which can contain ASCII letters, digits, and hyphens, excluding starting or ending with a hyphen. Labels are case-insensitive, so 'label' is the same as 'Label' or 'LABEL'. In the text format of a domain name, these labels are divided by a dot.

Domain names are frequently compared to real estate, serving as a base for constructing a website and often appreciating in value due to their potential for brand-building, advertising, and search engine optimization. In the past, domain registration was free when the Domain Name System was first introduced. Now, some companies may offer low-cost or free registration, but they usually require the domain to be hosted on their site with their advertising attached. Domain owners have the ability to create an unlimited number of subdomains, such as foo.example.org or foo.bar.example.org, for others to use.

A lot of popular domain names are already in use, so individuals must look for other suitable options. This can be done using search functions on the web, or through WHOIS and dig operating system tools. Numerous domain registrars have developed tools that suggest alternative domain names, scanning domain name databases and generating suggestions based on keywords provided by the user.

A domain name is part of a uniform resource identifier (URI), utilized to open websites. For instance:

A domain name can be linked to several IP addresses, enabling multiple servers to host a single website, thereby handling high traffic. Web hosting companies usually assign one or a few IP addresses to numerous domains, a practice known as shared web hosting. This necessitates each request to specify the relevant domain name, which can be achieved through the HTTP request header field "Host:" or Server Name Indication.