A domain name is the human-readable address that identifies a website, email service, or other internet resource. It is the text that people type into a browser, example.com, redirect.supply, google.com: to navigate to a destination on the internet. Behind every domain name is a DNS system that translates it into the numerical IP address of the server hosting the resource, making domain names the readable, memorable layer on top of the numeric addressing system that computers use to communicate.

Domain names exist because IP addresses are impractical for humans. The IP address 93.184.216.34 is the actual network address of the server hosting example.com. Both work, typing either into a browser reaches the same server, but the domain name is infinitely more useful for human communication. It is memorable, brandable, meaningful, and stable even as the underlying IP address changes.

Domain names are foundational to everything discussed across this glossary, every redirect rule operates on domain names, every DNS record maps a domain name to something, every SSL certificate is issued for a domain name, and every SEO ranking is associated with a domain name. Understanding domain names is understanding the most fundamental addressable unit of the web.

How a domain name works

A domain name is a human-readable label that the DNS system translates into the information needed to reach a network resource. When a browser receives a domain name, typed directly, clicked from a link, or navigated programmatically, it performs a DNS lookup to find the associated IP address. The DNS system queries the authoritative nameserver for the domain and retrieves the relevant DNS records: typically an A record containing the server’s IP address. The browser connects to that IP address and requests the resource.

The domain name itself has no direct connection to any server, it is a pointer that the DNS system resolves to the appropriate network destination. Changing the DNS records for a domain changes where the domain name points without changing the name itself. This separation between the name and the destination is what makes domain migrations, redirects, and DNS changes possible, the name stays the same while the destination changes.

Domain name structure

Domain names have a hierarchical structure that flows from right to left, from most general to most specific. Understanding the structure clarifies how domain names relate to DNS zones and how authority is delegated through the DNS hierarchy.

Top-level domain, TLD: the rightmost portion of a domain name. .com, .net, .org, .io, .co.uk. TLDs are the highest level of the DNS hierarchy below the root. Each TLD is managed by a registry, Verisign manages .com and .net, the Public Interest Registry manages .org. The registry maintains the list of all registered second-level domains under the TLD and publishes the delegation records that point to each domain’s nameservers.

Second-level domain, SLD: the label immediately to the left of the TLD. In example.com the second-level domain is example. In redirect.supply the second-level domain is redirect. The combination of second-level domain and TLD, example.com: is what is registered with a domain registrar and what most people think of when they say domain name.

Subdomain: any label to the left of the second-level domain. In www.example.com the subdomain is www. In blog.example.com the subdomain is blog. In shop.app.example.com there are two subdomain levels, shop and app. Subdomains are created by adding DNS records in the domain’s zone, they do not require separate registration.

The root: the DNS hierarchy has a root, represented as a trailing dot that is implicit in most domain names. example.com. with the trailing dot is the fully qualified domain name, FQDN, that explicitly includes the root. DNS software uses FQDNs internally. Most user-facing tools omit the trailing dot as it is implicit.

A complete domain name like www.blog.example.com reads right to left as: root (.) → TLD (com) → second-level domain (example) → subdomain (blog) → subdomain (www). Each level is delegated from the level above through NS records: creating the hierarchical structure that makes distributed DNS management possible.

Types of top-level domains

TLDs come in several categories reflecting their intended use, geographic association, or sponsoring organisation.

Generic TLDs, gTLDs: the original and most widely used TLDs without geographic restriction. The original set, .com, .net, .org, .edu, .gov, .mil: was established in the 1980s. .com was intended for commercial entities, .net for network infrastructure, .org for organisations, but these restrictions have never been enforced and .com in particular became the dominant TLD for websites of all types.

ICANN’s new gTLD program launched in 2013 dramatically expanded the TLD space, adding hundreds of new generic TLDs like .app, .dev, .store, .online, .io, .co, .supply, and many others. New gTLDs provide more availability for desirable short names and allow more topically specific domain names.

Country code TLDs, ccTLDs: two-letter TLDs assigned to specific countries and territories. .uk for the United Kingdom, .de for Germany, .fr for France, .jp for Japan, .au for Australia. ccTLDs are managed by national registries and may have residency or registration requirements. Some ccTLDs, .io, .co, .tv, .me: have become popular for generic use beyond their assigned country due to their short or meaningful letter combinations.

Sponsored TLDs, sTLDs: TLDs operated by specific organisations for defined communities. .edu for accredited US educational institutions, .gov for US government entities, .mil for the US military, .aero for the aviation industry, .museum for museums. Sponsored TLDs have eligibility requirements that limit who can register.

Infrastructure TLD: .arpa is reserved for internet infrastructure purposes, particularly for reverse DNS lookups. The in-addr.arpa and ip6.arpa zones are used for PTR record lookups that map IP addresses to domain names.

Domain name registration

Domain names are registered through domain registrars: companies accredited by ICANN or national registry authorities to sell domain name registrations. Registration creates a record in the TLD registry associating the domain name with the registrant’s details and the specified nameservers.

Registration period: domains are registered for one to ten years at a time. Registration must be renewed before expiry to maintain ownership. Expired domains enter a grace period during which the previous registrant can renew. After the grace period the domain is released for registration by anyone, potentially leading to domain expiry issues where valuable domains are lost.

WHOIS information: registration requires providing contact information, registrant name, organisation, address, email, phone number, that is published in the WHOIS database. Domain privacy services replace personal contact information with the privacy service’s details in WHOIS records, protecting registrant privacy while maintaining the required registration records.

Nameserver assignment: during registration the registrant specifies the nameservers for the domain, the servers that will be authoritative for the domain’s DNS. The registrar submits this information to the TLD registry which publishes the delegation records. The domain owner can change nameservers at any time through the registrar’s control panel.

Domain transfer: domains can be transferred between registrars, moving registration from one company to another while keeping the same domain name and DNS configuration. Transfers require an authorisation code from the current registrar and are subject to transfer lock periods that prevent rapid unauthorised transfers.

Domain names and redirects

Domain names are the fundamental unit of redirect management. Understanding how domain names relate to redirects clarifies the full picture of how redirect infrastructure works.

Redirect source and destination are domain-based: every redirect rule involves domain names, the redirect source is a URL under one domain and the redirect destination is a URL under the same or different domain. Domain redirects forward all traffic from one domain to another. Path-level redirects forward specific paths under a domain to specific destinations.

DNS connects domains to redirect infrastructure: before any HTTP redirect can be served the domain must be connected to redirect infrastructure through DNS. Updating A records or CNAME records in the domain’s DNS zone routes incoming requests to the redirect management server. The redirect server then applies configured redirect rules and returns the appropriate HTTP response.

Multiple domains in redirect management: redirect management often involves multiple domain names, an old domain being redirected to a new domain, multiple brand protection domains redirecting to a primary domain, or parked domains forwarding to an active site. Each domain name must be connected to redirect infrastructure independently, with appropriate DNS configuration, even if all domains ultimately redirect to the same destination.

Domain names and SEO equity: the SEO equity and link juice accumulated by a domain name are associated with that specific name. When a domain moves through a permanent redirect the equity transfers to the destination. When a domain expires without a redirect the equity is lost. Managing domain names thoughtfully, maintaining registrations, configuring redirects for retired names, monitoring for expiry, protects accumulated SEO value.

Domain names and SSL certificates

Every domain name used to serve content over HTTPS requires a valid SSL certificate issued for that specific domain name. The certificate proves the domain name is owned and controlled by the certificate holder, browsers verify the certificate when establishing HTTPS connections and display warnings for invalid or missing certificates.

Certificates cover specific domain names, an SSL certificate for example.com does not automatically cover www.example.com or shop.example.com. Certificates can cover multiple names through Subject Alternative Names, SAN, or through wildcard certificates that cover all subdomains of a domain.

For redirect management this means every domain connected to redirect infrastructure needs a valid SSL certificate, including secondary domains, parked domains, and brand protection domains being redirected to a primary domain. Without SSL a visitor typing https://olddomain.com receives a certificate error before the redirect can fire. Dedicated redirect management platforms handle SSL certificate provisioning automatically for connected domains, eliminating this complication.

Choosing a domain name

For anyone building a web presence, including a redirect management service or marketing site, domain name selection is a significant decision with long-term implications.

Memorability: a domain name should be easy to remember, spell, and type. Short names are generally more memorable than long ones. Names that match the brand or service are more intuitive than abstract combinations of letters.

TLD selection: .com remains the most recognised and trusted TLD for commercial use. For technical products .io, .dev, and .app have become widely accepted. For geographic targeting ccTLDs signal local relevance. The TLD should match the audience and use case.

Brand protection: registering common misspellings, alternative TLDs, and related names prevents competitors and bad actors from using them. These brand protection domains can be redirected to the primary domain, a standard use case for domain parking and global redirects.

Availability and uniqueness: desirable short .com names are largely registered. New gTLDs provide more options for short distinctive names. Trademark conflicts should be researched before registering, using a domain name that infringes on a trademark creates legal risk.

Longevity: domain names are long-term assets. A domain name that works today should work for the life of the brand. Choosing a name that accommodates future growth, not too specific to a current product or market, avoids needing to rebrand and change domains later.

Domain names and brand identity

Domain names are brand assets. The domain name is often the most visible and persistent element of an organisation’s online identity, appearing in URLs, email addresses, marketing materials, and countless other contexts. The relationship between domain names and brand identity creates specific considerations for domain management.

Rebranding and domain migration: when an organisation rebrands it typically acquires a new domain name that reflects the new brand identity. The old domain name must be maintained and redirected to the new one for as long as existing links, bookmarks, and brand recognition remain valuable, which can be years or indefinitely. This is one of the primary use cases for long-term domain redirect management.

Merger and acquisition: when companies merge the combined entity typically consolidates under one primary domain. The acquired company’s domain is redirected to the acquirer’s domain or to a new combined brand domain. Maintaining the redirect from the old domain preserves the SEO equity and link value built under the old brand, which can be significant.

Domain portfolio management: large organisations manage portfolios of domain names, primary domains, regional domains, product domains, brand protection domains, and historical domains. Each domain in the portfolio requires registration maintenance, DNS management, and appropriate redirect configuration. Centralised redirect management, handling all redirect rules for all domains in one place, simplifies portfolio management at scale.