Product Code Database
A top-level domain ( TLD) is one of the domain name at the highest level in the hierarchical Domain Name System of the Internet after the root domain. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last non-empty label of a fully qualified domain name. For example, in the domain name www.example.com, the top-level domain is .com. Responsibility for management of most top-level domains is delegated to specific organizations by the ICANN, an Internet multi-stakeholder community, which operates the Internet Assigned Numbers Authority (IANA), and is in charge of maintaining the DNS root zone.
IANA distinguishes the following groups of top-level domains:
Countries are designated in the Domain Name System by their two-letter ISO country code; Codes for the Representation of Names of Countries, ISO-3166, International Organization for Standardization. (May 1981) there are exceptions, however (e.g., .uk). This group of domains is, therefore, commonly known as country-code top-level domains (ccTLD). Since 2009, countries with non–Latin-based scripts may apply for internationalized country code top-level domain names, which are displayed in end-user applications in their language-native script or alphabet, but use a Punycode-translated ASCII domain name in the Domain Name System.
Generic top-level domains (formerly categories) initially consisted of .gov, .edu, .com, .mil, .org, and .net. More generic TLDs have been added, such as .info.
The authoritative list of current TLDs in the root zone is published at the IANA website at
/a>.
ICANN started to accept applications for IDN ccTLDs in November 2009, and installed the first set into the Domain Names System in May 2010. The first set was a group of Arabic names for the countries of Egypt, Saudi Arabia, and the United Arab Emirates. By May 2010, 21 countries had submitted applications to ICANN, representing 11 scripts.
| + Reserved Top-Level Domains | ||
| use in examples | ||
| use in invalid domain names | ||
| avoiding conflict with the traditional use of localhost as a hostname | ||
| use in tests | ||
| link-local host names that can be resolved via the multicast DNS name resolution protocol | ||
| self-authenticating names of Tor onion services | ||
| private application use | ||
| .alt | alternative (non-DNS) namespaces |
Other historical TLDs are .cs for Czechoslovakia (now using .cz for Czech Republic and .sk for Slovakia), .dd for East Germany (using .de after reunification of Germany), .yu for SFR Yugoslavia and Serbia and Montenegro (now using .ba for Bosnia and Herzegovina, .hr for Croatia, .me for Montenegro, .mk for North Macedonia, .rs for Serbia and .si for Slovenia), .zr for Zaire (now .cd for the Democratic Republic of the Congo), and .an for Netherlands Antilles (now .aw for Aruba, .cw for Curaçao and .sx for Sint Maarten). In contrast to these, the TLD .su has remained active despite the collapse of the Soviet Union that it represents. Under the chairmanship of Nigel Roberts, ICANN's ccNSO is working on a policy for the retirement of that have been removed from ISO 3166.
An older proposal consisted of seven new gTLDs: arts, firm, .info, nom, rec, .shop, and .web. Later .biz, .info, .museum, and .name covered most of these old proposals.
During the 32nd International Public ICANN Meeting in Paris in 2008, ICANN started a new process of TLD naming policy to take a "significant step forward on the introduction of new generic top-level domains". This program envisioned the availability of many new or already proposed domains, as well as a new application and implementation process. Observers believed that the new rules could result in hundreds of new gTLDs being registered. ICANN Board Approves Sweeping Overhaul of Top-level Domains, CircleID, 26 June 2008.
On 13 June 2012, ICANN announced nearly 2,000 applications for top-level domains, which began installation throughout 2013. The first seven – bike, clothing, guru, holdings, plumbing, singles, and ventures – were released in 2014.
Investigation into the conflicts was conducted at ICANN's request by Interisle Consulting. The resulting report was to become known as the Name Collision issue, which was first reported at ICANN 47.
Dotless domains are top-level domains that take advantage of that fact, and implement A record, AAAA record or MX record DNS records to serve webpages or allow incoming email directly on a TLD – for example, a webpage hosted on http://example/, or an email address user@example.
ICANN and IAB have spoken out against the practice, classifying it as a security risk among other concerns. ICANN's Security and Stability Advisory Committee (SSAC) additionally claims that SMTP "requires at least two labels in the FQDN of a mail address" and, as such, mail servers would reject emails to addresses with dotless domains.
ICANN has also published a resolution in 2013 that prohibits the creation of dotless domains on . , however, fall largely under their respective country's jurisdiction, and not under ICANN's. Because of this, there have been many examples of dotless domains on ccTLDs in spite of ICANN's vocal opposition.
As of September 2023, that is the case of:
()
albeit with an invalid certificate.
Other ccTLDs with A or AAAA records, as of September 2023, include: .cm, .tk and .ws.
A similar query to orgs presented above can be made for ai, which shows A and MX records for the TLD:
Historically, many other ccTLDs have had A or AAAA records. On 3 September 2013, as reported by the IETF, they were the following: .ac, .dk, .gg, .io, .je, .kh, .sh, .tm, .to, and .vi.
This requirement is meant to avoid domain name collisions when new TLDs are registered. For example, programmers may have used custom local domains such as foo.bar or test.dev, which would both collide with the creation of gTLDs .bar in 2014 and .dev in 2019.
While this does create apex DNS records of type A and MX, they do not qualify as a dotless domain, as the records should not point to real servers. For instance, the A record contains the IP 127.0.53.53, a loopback address (see IPv4 § Addressing), picked as a mnemonic to indicate a DNS-related problem, as DNS uses port 53.
Most of these networks have long since ceased to exist, and although UUCP still gets significant use in parts of the world where Internet infrastructure has not yet become well established, it subsequently transitioned to using Internet domain names, and pseudo-domains now largely survive as historical relics. One notable exception is the 2007 emergence of SWIFTNet Mail, which uses the swift pseudo-domain.
The anonymity network Tor formerly used the top-level pseudo-domain .onion for onion services, which can only be reached with a Tor client because it uses the Tor onion routing protocol to reach the hidden service to protect the anonymity of users. However, the pseudo-domain became officially reserved in October 2015. i2p provides a similar hidden pseudo-domain, .i2p, and Namecoin uses the .bit pseudo-domain.
| + Examples of the over 1,500 TLDs | ||
| .arpa | Infrastructure | Internet Architecture Board; restricted |
| .blue | Generic | Identity Digital; unrestricted |
| .ovh | Generic | OVH; run by AFNIC, unrestricted |
| .name | Restricted generic | VeriSign; unrestricted |
| .ac | Country-code | Internet Computer Bureau; unrestricted |
| .zw | Country-code | Postal and Telecommunications Regulatory Authority of Zimbabwe; run by TelOne Zimbabwe; unrestricted |
| .aero | Sponsored | Société Internationale de Télécommunications Aéronautiques; unrestricted |
| .ไทย | Internationalized country-code | THNIC |
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