Domain Names and Extensions Explained
- Every URL has four components: protocol (https://), subdomain (www.), second-level domain (your brand name), and TLD (.com)
- Three hierarchical types exist: top-level domains (TLDs), second-level domains (the name you register), and third-level domains (subdomains like blog. or shop.)
- Over 1,500 active TLDs exist in the IANA root zone database as of 2026 — up from just 6 when the internet launched in 1985
- Country-code TLDs can generate national income: Tuvalu earns roughly one-twelfth of its GDP from .tv domain sales
- .com dominates with approximately 37% of all registered domains — around 160 million of 350+ million total registrations globally
- The right extension depends on your industry, audience, and whether the .com equivalent is strategically achievable
Understanding the types of domain names is foundational to any online presence. Whether you are choosing an extension for a new business, researching TLDs for an AI startup, or simply trying to understand what all those letters after the dot mean, this guide covers everything — from how domain names are structured to a complete domain name extensions list with costs, use cases, and a decision framework for choosing the right extension.
The Anatomy of a URL
Every web address consists of multiple components, each serving a distinct function:
| Component | Example | Purpose |
|---|---|---|
| Protocol | https:// | Defines how data transfers between browser and server; https:// signals encrypted connection |
| Subdomain (3rd-level) | www. | Prefix added before the domain; customizable (blog., shop., support.) |
| Second-level domain (SLD) | nameexperts | The registrable brand name — the most valuable, brandable element of any web address |
| Top-level domain (TLD) | .com | The extension after the final dot; defines category (.com, .org) or country (.uk, .de) |
The Three Types of Domain Names
Domain names organize into three hierarchical levels, each with a distinct role:
- Top-Level Domains (TLDs) — the extension at the far right of the URL (.com, .org, .uk). TLDs are the foundation of the entire domain name system and form the basis of all domain categories.
- Second-Level Domains (SLDs) — the registrable name immediately to the left of the TLD ("nameexperts" in nameexperts.com). This is the most valuable component for branding and the element you actually own when you register a domain.
- Third-Level Domains (Subdomains) — prefixes added before the SLD, such as "blog" in blog.nameexperts.com or "shop" in shop.nameexperts.com. Subdomains are free to create via DNS settings and require no separate domain registration.
The 4 Categories of Top-Level Domains
| Type | Abbreviation | Examples | Open Registration? | How Many? |
|---|---|---|---|---|
| Generic TLD | gTLD | .com, .org, .net, .info, .io, .ai, .app | Yes (most) | 1,200+ (post-2011) |
| Country-Code TLD | ccTLD | .uk, .de, .ca, .ai, .tv, .io, .co | Varies by country | ~300 |
| Sponsored TLD | sTLD | .edu, .gov, .mil, .int, .museum | No — restricted to qualifying entities only | ~14 |
| Infrastructure | (ARPA) | .arpa | No — technical/operational use only | 1 |
Generic TLDs: From 6 to 1,500+
When the internet's domain name system launched in 1985, only six generic TLDs existed: .com (commercial), .org (organization), .net (network), .edu (education), .gov (government), and .mil (military). In 2011, ICANN opened the namespace to new generic TLDs, triggering an expansion from 22 to over 1,500 active extensions by 2026. New gTLDs cover industries (.tech, .finance, .law), activities (.blog, .shop, .app), cities (.nyc, .london), and brand-specific extensions (.google, .apple).
Domain Name Extensions List: The Most Important TLDs
| Extension | Type | Best For | Annual Cost | Open? |
|---|---|---|---|---|
| .com | gTLD | All businesses; global default extension | $10–$20 | Yes |
| .org | gTLD | Nonprofits, charities, open-source projects | $9–$15 | Yes |
| .net | gTLD | Technology companies, networks, ISPs | $10–$18 | Yes |
| .io | ccTLD (British Indian Ocean Territory) | Tech startups, developer tools, SaaS products | $25–$50 | Yes |
| .ai | ccTLD (Anguilla) | AI companies, machine learning startups | $50–$100 | Yes |
| .co | ccTLD (Colombia) | Startups and global companies; .co = company shorthand | $25–$35 | Yes |
| .app | gTLD | Mobile apps, SaaS platforms (HTTPS required by spec) | $14–$20 | Yes |
| .tech | gTLD | Technology companies, IT service providers | $30–$50 | Yes |
| .shop / .store | gTLD | E-commerce, retail businesses | $20–$60 | Yes |
| .uk / .co.uk | ccTLD (United Kingdom) | UK-based businesses targeting UK audiences | $5–$12 | Yes |
| .de | ccTLD (Germany) | Germany-based businesses and brands | $5–$10 | Yes (German presence preferred) |
| .edu | sTLD | Accredited U.S. educational institutions only | $3–$5 | No — EDUCAUSE verification required |
| .gov | sTLD | U.S. government entities only | $400 | No — U.S. government only |
Country-Code TLDs That Became Global Industry Extensions
Some ccTLDs have transcended their country-of-origin to become globally recognized extensions for specific industries:
- .io (British Indian Ocean Territory) — adopted by tech startups; "io" suggests input/output in programming. Google treats it as a generic TLD for SEO purposes.
- .ai (Anguilla) — the defining extension of the artificial intelligence industry. The February 2026 AI.com sale for $70 million confirmed its premium status. Learn more about .ai domains.
- .tv (Tuvalu) — adopted by streaming platforms and media companies; Tuvalu earns roughly one-twelfth of its national income from .tv domain registrations
- .co (Colombia) — marketed globally as a shorthand for "company"; widely adopted by startups and international businesses
- .me (Montenegro) — used for personal websites, professional portfolios, and individual brand building
Need Help Choosing the Right Domain Extension?
Name Experts advises brands on TLD strategy and acquires premium domain names across all major extensions — from classic .com to emerging .ai and .io names. Talk to an expert before you commit.
How to Choose the Right Domain Extension
| Your Situation | Best Extension | Rationale |
|---|---|---|
| General business or e-commerce | .com | Maximum trust, global recognition, best for direct type-in traffic |
| Nonprofit or charity | .org | Signals mission-driven identity; builds instant trust with donors and community |
| Tech startup or SaaS tool | .io or .tech | Strong tech association; many short, memorable names still available |
| AI or machine learning company | .ai | Industry-standard signal; Google treats it as generic for global SEO |
| UK-focused business | .co.uk | Geographic signal boosts local UK search rankings significantly |
| Mobile app or platform | .app | Industry-specific; HTTPS required by specification (good security default) |
| Your ideal .com is taken | Premium .com acquisition | A domain broker can often acquire the .com for less than you expect |
Subdomains: When to Use Third-Level Domains
Subdomains let you create distinct sections of your website without registering additional domains. Common examples:
- blog.yoursite.com — when your blog runs on a separate CMS from your main site
- shop.yoursite.com — when your e-commerce platform is separate from your marketing site
- support.yoursite.com — for customer help portals running on tools like Zendesk or Freshdesk
- app.yoursite.com — for web application interfaces separate from marketing pages
From an SEO perspective, subdomains may be treated as separate sites by Google, meaning they may not inherit the full link equity of your main domain. For content closely related to your core site, subdirectories (yoursite.com/blog/) often perform better SEO-wise. Reserve subdomains for genuinely separate applications or platforms.
How Many Domain Extensions Are There?
As of 2026, the IANA root zone database contains over 1,500 active top-level domains — a number that has grown substantially since ICANN's 2011 policy change opened the namespace to new gTLDs. The global domain registration count exceeds 350 million active domains across all extensions, led by .com at approximately 160 million registrations.
Frequently Asked Questions
As of 2026, there are over 1,500 active domain extensions (TLDs) in the IANA root zone database. Before 2011, only 22 generic TLDs existed, including familiar options like .com, .org, and .net. When ICANN opened the namespace, over 1,200 new generic TLDs were introduced, covering industries (.tech, .finance), activities (.blog, .shop), and geographic regions (.london, .nyc). Combined with approximately 300 country-code TLDs, the full domain name extensions list continues to grow as new applications are approved.
Domain names are organized into three hierarchical types. Top level domains (TLDs) are the extension after the final dot, such as .com or .org. Second-level domains are the brandable name you register -- for example, "nameexperts" in nameexperts.com. Third-level domains, also called subdomains, are prefixes added before the second-level domain, like "www" or "shop" in shop.nameexperts.com. Each type serves a different function in the Domain Name System hierarchy.
A domain extension (also called a TLD) is just the suffix after the dot -- such as .com, .org, or .ai. A domain name is the complete, registrable address that includes both the second-level domain (your chosen name) and the TLD. For example, in "nameexperts.com," the domain extension is ".com" and the full domain name is "nameexperts.com." When people refer to a domain name extensions list, they are typically looking at the available TLD options they can pair with their desired brand name.
The .com extension remains the most trusted and widely recognized domain extension for businesses worldwide, accounting for roughly 37% of all registered domains. If your ideal .com is unavailable, strong alternatives include country-code extensions for local businesses (.co.uk, .ca, .com.au), industry-specific new gTLDs (.tech, .agency, .store), and emerging extensions like .ai for technology companies. The best extension depends on your industry, target audience, and whether a premium .com acquisition through a domain broker might be worth the investment.
Yes, country-code TLDs (ccTLDs) can influence local SEO. Google treats ccTLDs as a geographic signal, which can boost your rankings for searches originating in that specific country. A .co.uk domain will have an advantage in UK search results, while a .de domain signals relevance to German searchers. However, ccTLDs can limit your visibility in other countries. If you serve a global audience, a gTLD like .com paired with hreflang tags and Google Search Console geo-targeting is typically the better approach.
Subdomains are third-level domains that appear before your main domain name -- for example, blog.yoursite.com or shop.yoursite.com. They are useful for separating distinct sections of your website that may run on different platforms, such as an e-commerce store or a knowledge base. Subdomains are free to create through your hosting provider and do not require additional domain registration. However, from an SEO perspective, subdomains are sometimes treated as separate entities by search engines, so many SEO professionals recommend using subdirectories (yoursite.com/blog/) instead when the content is closely related to your main site.
