science

List of Internet top-level domains

List of Internet top-level domains is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand List of Internet top-level domains rather than just read about it. In short: This list of Internet top-level domains (TLD) contains top-level domains, which are those domains in the DNS root zone of the Domain Name System of the Internet. A list of the top-level domains by the Internet Assigned Numbers Authority (IANA) is maintained at the Root Zone Database.

Key takeaways

List of Internet top-level domains belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect List of Internet top-level domains to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of List of Internet top-level domains from memory before moving on to harder problems.

Reference excerpt

This list of Internet top-level domains (TLD) contains top-level domains, which are those domains in the DNS root zone of the Domain Name System of the Internet. A list of the top-level domains by the Internet Assigned Numbers Authority (IANA) is maintained at the Root Zone Database. IANA also oversees the approval process for new proposed top-level domains for ICANN. As of February 2026, the IANA root database includes 1593 TLDs. This database also includes 156 that are not assigned (revoked or retired) and 11 test domains, all of which are not represented in IANA's TLD listing nor in the root.zone file (the file also includes one root domain).

Types

IANA distinguishes the following groups of top-level domains:

infrastructure top-level domain (ARPA) generic top-level domains (gTLD) generic-restricted top-level domains (grTLD) sponsored top-level domains (sTLD) country code top-level domains (ccTLD) test top-level domains (tTLD)

Original top-level domains Seven generic top-level domains were created early in the development of the Internet, prior to the creation of ICANN in 1998.

Infrastructure top-level domains

Country code top-level domains

As of 20 May 2017, there were 255 country-code top-level domains, purely in the Latin alphabet, using two-character codes. As of June 2022, the number was 316, with the addition of internationalized domains.

Proposed internationalized ccTLDs

ICANN-era generic top-level domains Target market: intended use Operator: entity the registry has been delegated to DNSSEC: presence of DS records for Domain Name System Security Extensions

English

Chinese

French

German

Hindi

Italian

Portuguese

Spanish

Internationalized generic top-level domains All of these TLDs are internationalized domain names (IDN) and support second-level IDNs.

Arabic script

Chinese characters

Cyrillic script

Japanese characters

Other scripts

Geographic top-level domains

Africa

Asia

Europe

North America

Oceania

South America

Internationalized geographic top-level domains

Brand and corporate top-level domains

Internationalized brand top-level domains

Special-use domains ICANN/IANA has created some special-use domain names which are meant for technical purposes. ICANN/IANA owns all of the special-use domain names.

Non-IANA domains Besides the TLDs managed (or at least tracked) by IANA or ICANN, other independent groups have created, or had attempted to create, their own TLDs with varying technical specifications, functions, and outcomes.

Microsoft Windows Within Microsoft Windows there are some special purpose domain names that partially conflict with publicly assigned ones.

Internet Engineering Task Force proposals for local TLDs The Internet Engineering Task Force (IETF) has submitted several requests for comments on TLDs that could be used to represent local devices and services.

Blockchain-registered Blockchain-based domains are registered and exchanged using a public blockchain like Ethereum. Oftentimes, these domains serve specific functions such as creating human-readable references to smart contract addresses used in DApps or personal wallet addresses. Generally, these non-standard domains are unreachable through the normal DNS resolution process and instead require clients to use some sort of transparent web proxy or gateway to access them

Alternate roots In the case of alternative DNS roots, organizations or projects make use of the same mechanisms of the DNS but instead take on the role of ICANN in managing and administering an entirely separate root zone, thus having the ability to create new TLDs independently. However, this doesn't make these domains any less isolated from the rest of the internet, as the ability for clients to resolve them theoretically only requires switching to a recursive DNS resolver that recognizes and serves records underneath the alternate root zone.

See also Top-level domain Country code top-level domain Generic top-level domain Pseudo-top-level domain IDN Test TLDs ISO 3166-1 alpha-2, the standard for two-letter country codes, which most ccTLDs are based on Proposed top-level domain Second-level domain, information about .co.jp, .co.uk, .co.kr, .co.nf, etc. Public Suffix List

Explanatory notes

Citations

External links IANA's list of TLDs in machine-readable format Verisign's "Domain Name Industry Brief" site, with reports and dashboards The Public Suffix List / PSL – Maintained by Mozilla Registry Agreements at ICANN Registry Agreement Termination Info Page at ICANN

Worked examples

Example 1 — a first encounter with List of Internet top-level domains

Start with the simplest possible case. Write down what List of Internet top-level domains claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to List of Internet top-level domains before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about List of Internet top-level domains ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of List of Internet top-level domains

In research: List of Internet top-level domains appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses List of Internet top-level domains in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: List of Internet top-level domains is common in secondary-school and first-year university syllabi. It links to neighbouring topics Country codes, International telecommunications, Internet-related lists, so understanding it makes those chapters shorter.
In everyday life: Look for List of Internet top-level domains outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study List of Internet top-level domains in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what List of Internet top-level domains means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain List of Internet top-level domains out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is List of Internet top-level domains in simple terms?

Why does List of Internet top-level domains matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study List of Internet top-level domains?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on List of Internet top-level domains.