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ICANN and the International Organization for Standardization (ISO)

A Common Interest in ISO Standard 3166


The ISO 3166 standard is used for the definition of eligible designations for ccTLDs and to determine the eligibility for an IDN ccTLD string. ICANN maintains a technical relationship with entities responsible within ISO for maintaining the standard. The Policy Development Support Department is responsible for ICANN’s maintaining the relationship.

ICANN – ISO Working Relationship on ISO 3166 Matters

The use of the ISO Standard 3166 for the definition of country code Top Level Domains began in 1986. The practice was first mentioned in RFC 920 (October 1984). The practice was also mentioned in RFC 1032 (November 1987) and with the further use of the alpha-2 codes prominently documented in RFC 1591 (March 1994). In 2000, the ICANN Board of Directors recognized the ISO 3166 Maintenance Agency as the authoritative entity for country code designations and officially adopted the use of ISO 3166-1 and the 3166-MA exceptional reserved list as the set of eligible designations for ccTLD assignment (September 2000). ISO 3166 is also used to determine the eligibility for an IDN ccTLD string under the IDN ccTLD Fast Track process. 

Historically, there have been occasional contacts between ICANN and the ISO 3166/MA. More frequent interactions take place between Internet Engineering Task Force (IETF) and the ISO/IEC joint technical committee (JTC1) and SC via liaisons appointed by the IAB. See. for more details about this.

In 2003, the ISO extended an invitation to ICANN to join 3166/MA as ICANN was seen as one of the major users of ISO 3166 Standard. Since 2006, ICANN has participated in the technical work of the ISO 3166 MA, and never votes on matters that relate to selection of country codes. ICANN’s main focus has been on technical issues relating to proposed changes to the ISO 3166 that may have an effect on the use by ICANN’s administration of the IANA Function in designating ccTLD codes and the broader issues pertaining to the use of the ISO 3166 standard in the ICANN environment. Recently, ISO expressed an interest in the possibility to establish a liaison between ICANN and ISO TC 46/WG 2. 

Based on participation in the ISO MA and the need for a good working relationship with ISO and the organizations participating in it, ICANN has established a Category D liaison with ISO’s Technical Committee 46/Working Group 2 (TC 46/WG 2). The Policy Development Support Department is responsible for ICANN’s representation at the ISO’s TC 46/WG 2 and the ISO 3166 MA.  

ISO 3166 and its maintenance

The ISO defines international standards for many areas of trade and industry, often after long and complicated negotiations. One of the ISO standards, the ISO 3166 international standard for Codes for the representation of names of countries and their sub-divisions Part 1: country codes (ISO 3166-1), is used to define the country-code Top-Level Domains (ccTLDs), e.g., ".fr", ".za", ".au", ".br", or ".jp". in the Internet domain name system.

ISO 3166

The ISO Standard 3166 defines Codes for the representation of names of countries and their subdivisions. ISO 3166 consists of the following 3 parts:

  • Part 1: Country codes
  • Part 2: Country subdivision code
  • Part 3: Code for formerly used names of countries

These codes are used for a broad range of applications, for example but not limited to marking of freight containers, postal use and as a basis for standard currency codes. The ISO 3166-1 country Alpha codes consist of two or three letters from the 26-character Roman alphabet (A-Z and ignoring diacritic signs). For the Internet Domain name system only the two letter (Alpha-2 code) list is used to define country-code Top Level Domains.

Additions to the ISO 3166 list are only made on the basis of information from the United Nations Headquarters, or, in some cases upon a request of a member of the ISO 3166/MA. Deletions are made under the same provisions. Alterations to a country name of code element are primarily based on information from United Nations Headquarters.

ISO 3166 Technical Committee 46/Working Group 2

Much of the work on ISO standards is done by technical committees (TCs), with advice from specialized working groups.  The ISO 3166 standard falls under the auspices of Technical Committee 46 (TC 46) “Information and Documentation”. One of its working groups — WG 2 — deals with “coding of country names and related entities”. The technical committee consists out of 35 national standardization institutes and 37 observing. Both TC 46 and the specialized working groups also have organizations in liaison. ICANN is one of the organizations in liaison with WG 2. The role of WG 2 is to:

  • Propose changes to guidelines for the maintenance of ISO 3166 standard;
  • Review and advise on updates of the standard;
  • Define work items and propose possible extensions of standard.

ISO 3166 Maintenance Agency (MA)

The ISO 3166 standard is maintained and updated by the MA, following its Guidelines for the Maintenance of ISO 3166. The MA consists of 10 individually named members, 5 of them from national standards organizations and the other half from major users, international organizations who have been invited to nominate a member, one of which is ICANN.

The main functions of the MA are to:

  • Add and to eliminate country and country subdivision names and to assign code elements as needed;
  • Update and disseminate lists of country and country subdivision names, code elements and their definitions;
  • Issue newsletters announcing changes to the code tables;
  • Administer the reservation of code elements.

The secretariat of the ISO 3166/MA publishes the standard, newsletters updating ISO 3166 and maintains a website at the URL The website contains a subset of the standard, mainly from part 1, and auxiliary information such as a FAQ.

Domain Name System
Internationalized Domain Name ,IDN,"IDNs are domain names that include characters used in the local representation of languages that are not written with the twenty-six letters of the basic Latin alphabet ""a-z"". An IDN can contain Latin letters with diacritical marks, as required by many European languages, or may consist of characters from non-Latin scripts such as Arabic or Chinese. Many languages also use other types of digits than the European ""0-9"". The basic Latin alphabet together with the European-Arabic digits are, for the purpose of domain names, termed ""ASCII characters"" (ASCII = American Standard Code for Information Interchange). These are also included in the broader range of ""Unicode characters"" that provides the basis for IDNs. The ""hostname rule"" requires that all domain names of the type under consideration here are stored in the DNS using only the ASCII characters listed above, with the one further addition of the hyphen ""-"". The Unicode form of an IDN therefore requires special encoding before it is entered into the DNS. The following terminology is used when distinguishing between these forms: A domain name consists of a series of ""labels"" (separated by ""dots""). The ASCII form of an IDN label is termed an ""A-label"". All operations defined in the DNS protocol use A-labels exclusively. The Unicode form, which a user expects to be displayed, is termed a ""U-label"". The difference may be illustrated with the Hindi word for ""test"" — परीका — appearing here as a U-label would (in the Devanagari script). A special form of ""ASCII compatible encoding"" (abbreviated ACE) is applied to this to produce the corresponding A-label: xn--11b5bs1di. A domain name that only includes ASCII letters, digits, and hyphens is termed an ""LDH label"". Although the definitions of A-labels and LDH-labels overlap, a name consisting exclusively of LDH labels, such as"""" is not an IDN."