Extensions and their registries

Module 1: How the domain system works · Reading time: 9 minutes

Learning objective: After this lesson you can tell the types of extensions apart, name the registry for each extension and explain why the rules differ per extension.

Key concepts: extension, TLD, ccTLD, gTLD, new gTLDs, IANA, ICANN, registry, requirements per extension

The last part of the name

Every domain name ends in an extension: .nl, .de, .com, .shop. The technical term is top-level domain or TLD. How the rest of a name is built (labels, subdomains, the dot at the end) is covered in the DNS course, lesson 1.2. This lesson is about something else: the extension decides whose rules apply to your name.

You only notice this when it matters. Who may register the name? Which characters are allowed? How long do you have to get back a name you forgot to renew? What is the code for transferring it called? The answer to all of these is: it depends on the extension. A .nl name and a .com name look the same to a visitor, but behind the scenes very different rules apply.

Country extensions and generic extensions

There are two main types of extensions.

• ccTLDs (country code TLDs) are two-letter country codes: .nl for the Netherlands, .de for Germany, .be for Belgium. .eu also belongs to this group, even though the European Union is not a country.
• gTLDs (generic TLDs) are general extensions such as .com, .org and .net. In recent years many new gTLDs have been added: extensions for a sector or a place, such as .shop, .app or .amsterdam.

The difference is more than a label. For gTLDs, one worldwide organisation sets the basic rules. For a country extension, the manager in that country largely decides the rules itself.

Who keeps the list?

At the top of the system are two organisations.

• IANA keeps track of which extensions exist and who manages each one. IANA is part of ICANN.
• ICANN is an international non-profit organisation. ICANN sets the rules for gTLDs: what is made public about a registrant, how a transfer works, when your registrar must warn you that your domain is about to expire. ICANN does not set these rules for country extensions such as .nl.

Below that, each extension has exactly one registry: the organisation that keeps the register for that extension and sets its rules. The best-known ones for businesses in the Netherlands and Belgium:

A few figures to show the scale (as of November 2026): there are over 6 million .nl names, over 18 million .de names and over 3.6 million .eu names.

Good to know: you almost never register directly with a registry. You go to a registrar, which passes the registration on for you (lesson 1.3). The registry does see you as the registrant, and its rules apply to you too.

The rules differ per extension

Below are a few differences you will come across more often in this course. You don't need to learn them by heart yet; the point is to see how big the differences are.

Who may register. Anyone may register a .nl name, wherever in the world you live. If you live outside the Netherlands, SIDN's office address in Arnhem counts as your address for service of official documents. Someone from outside Germany may also register a .de name; you only have to appoint a German address for legal post if someone with a trademark or name right asks for it. Anyone may register a .be name. The requirements for .eu are stricter: you must be a citizen of an EU country, Iceland, Liechtenstein or Norway, or live in one of those countries, or your organisation must be established there.

Which characters are allowed. A .nl name may only contain the letters a to z, digits and the hyphen. In .de and .be, letters with accents and umlauts are also allowed (lesson 2.4).

Contacts. For .nl you must provide an administrative and a technical contact in addition to the registrant. Since 2018, DENIC only registers the registrant for .de. For .com and other gTLDs, the administrative contact was abolished in August 2025 (module 3).

After cancelling or expiring. A cancelled .nl name goes into quarantine for 40 days, just like a .eu or .be name. A .de name has 30 days in which only the last registrant can get it back. A .com name goes through a series of phases, each with its own name (module 5).

The transfer code. For .nl it is called the token, for .de the AuthInfo, for .eu the transfer authorisation code, and for .be DNS Belgium sends it by email itself (module 6).

The lesson here: for every extension you are considering, read the registry's rules, or at least the summary your registrar provides. What is normal for one extension may be forbidden for another.

Why this matters to you as a registrant

Say Example Bakery in Utrecht (Netherlands) has example.com for its website and also wants a .nl name and a .eu name. Then three sets of rules apply: those of Verisign and ICANN for the .com name, those of SIDN for the .nl name and those of EURid for the .eu name. If the bakery loses one name through a forgotten renewal, how long it has to get it back differs per extension. And if it later moves to another registrar, it will need three kinds of codes.

A common mistake is thinking that "the registry" is one body that handles everything. If you get an email from "the domain register" asking you to pay quickly, check who the sender really is. SIDN, for example, does not sell .nl names to registrants itself. Lesson 7.1 goes into this further.

In practice: how it works at WebOké

If you look up a name at WebOké with Domain search, you will see "Other extensions for" your name below the result: fifteen popular extensions at once, each showing whether it is available or taken. With "Show all available extensions" you see the rest. That is handy for comparing, but it tells you nothing about the rules for each extension: those differ per registry. Searching works in a similar way at other registrars.

Summary

• The extension (TLD) decides which rules apply to your domain name.
• ccTLDs are country codes such as .nl, .de and .be (and .eu); gTLDs are generic extensions such as .com and .org, plus the new gTLDs.
• IANA keeps track of which extensions exist; ICANN sets the rules for gTLDs, not for country extensions.
• Each extension has one registry: SIDN, DENIC, DNS Belgium, EURid, Verisign, Public Interest Registry.
• Who may register, which characters are allowed, what happens after expiry and how transfers work: it differs per extension.

Quiz

Exercise

Exercise A1.2: Which registry? (case study). Example Bakery is listing all its domain names and wants to know, for each name, which registry sets the rules. It has names with six extensions: .nl, .de, .eu, .be, .com and .org. For each extension, choose the registry from the drop-down list. Each drop-down list contains the same six options:

• SIDN
• DENIC
• EURid
• DNS Belgium
• Verisign
• Public Interest Registry

The program compares your answers with a fixed key. All six correct is green, five correct is orange. If you make a mistake, you can try again.

Further reading

• What is SIDN and where are .nl domains registered?
• Who is EURid and who registers .EU names?
• The History of the Domain Name
• Free DNS course 1.2: How a domain name is structured