What Is a TLD? Top-Level Domains Definition and Guide

Even if the acronym “TLD” is unfamiliar, you’re likely familiar with top-leveldomains. You know the big ones:.com,.org, .gov,.co.uk, and so on. You may even know some that are off the beaten path, like .lol, .wtf, or even .christmas.

There were just nine of these suffixes attached to website names in 1985, when the internet existed behind the closed walls of government and corporations. But after three and a half decades of internet maturation, as ofJune 2020, there were 1,514 of them. So what are TLDs actually for, and what do they do?

What is a TLD?

A top-level domain (TLD) is the part of a URL that comes after the first dot in the domain name. The most popular TLD is .com, but there are many, many more.

TLDs serve a few different purposes, one of which is to help make a web address more memorable. They may also indicate certain affiliations with the government, academic institutions, various countries around the world, and more.

Think of .com as the go-to multipurpose TLD that works for all kinds of commercial entities representing themselves online. A more esoteric TLD like .xyz might be useful to evoke creativity and intrigue in a URL. German companies might want to use .de, while Canadians might want to use .ca. The best uses of a particular TLD are those that enhance an entity’s context, letting visitors know where they are located or otherwise revealing some character of the content that lives at a given URL.

How do TLDs work?

You can’t talk about TLDs without talking about the organizations of people that make them work, like theInternet Engineering Task Force,or theInternet Corporation for Assigned Names and Numbers (ICANN).ICANNis an American nonprofit organization that’s responsible for coordinating and maintaining several important databases related to the namespaces and numerical spaces of the internet. This organization holds theresponsibility for managementwhen it comes to TLDs, from the new ones that are allowed to exist to the proposed ones that are not.

With a stated goal of ensuring “a stable, secure, and unified global Internet,”ICANNis managed by a 16-member board of directors. Eight are selected by a nominating committee, six represent its supporting organizations that advise on all matters pertaining to domain names and IP addresses, one is a seat filled by an at-large organization, and one is the board-appointed president.

WhereICANNis the human and qualitative side oftop-level domains, the technicals live within theDNS, ordomain name system. DNS is probably most readily understood as a phone book of the internet—they interpret URLs like “google.com” or “unicef.org” into IP addresses that tell a computer where to look in order to retrieve certain information. Different TLDs on the same URL text will yield completely different IP addresses and completely different sites. Consider google.com and google.org—the same name with a different TLD will yield two very different sites. DNS is the figurative secret sauce at work here, bridging the gap between human information, like the name of a website, and the ones and zeroes that a computer depends on in order to render that site.

ICANNmanages the Internet Assigned Numbers Authority (IANA), an internet standards organization that oversees the world’s IP address allocation and root zone management in thedomain name system等。IANA负责根的名字erver operators andICANNpolicy makers.

主要类型的顶级域名

TLDs exist at the intersection of internet identity and internet technology, and a site administrator’s choice in TLD is quite intentional, whether it’s a generic TLD, one that indicates a particular geographical area, or even a sponsored top-level domain.

1. Infrastructure top-level domain

   This category consists of just one domain, .arpa (“address and routing parameter area”). It is designated exclusively for internet infrastructure purposes and is managed by IANA.
   
   

2. Generic top-level domain

   (gTLD)This category predominantly consists of four giants: .com, .net, .info, and .org.Generic TLDsmake up the lion’s share of registered domain names precisely because they are unspecialized and available to just about anyone.
   
   

3. Generic restricted top-level domains (grTLD)

   These domains are managed under officialICANNaccredited registrars and require certain proof of eligibility in order to register them. The TLDs .name and .pro are two examples.
   
   

4. Sponsored top-level domain

   (sTLD)These are proposed (and sponsored) by private entities representing a specific community that the website serves. Examples include .mil, .gov, or .aero, which is sponsored by members of the air transportation industry.
   
   

5. Country-code top-level domain (ccTLD)

   AccTLDis a two-letter domain used to designate a country or territory. For example, Japan is .jp.
   
   

6. Internationalized country code top-level domains (IDN ccTLD)

   This category of TLD exists to designate internet-connected countries that do not use a Latin character set in their writing, like Greek, Hebrew, or Chinese. Consider .jp for Japan or .il for Israel.
   
   

7. Test top-level domains (tTLD)

   This refers to just one TLD, .test. Perhaps predictably, this is for use in testing software. It’s existed since June 1999, but will never interface with the globaldomain name system.

At the end of the day, TLDs are merely the very last part of a domain name. But they’re also an important part of the infrastructure that makes the internet more useful and accessible.