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IDNs: Final Report on Three-Character Requirement and Variant Management Now Available for Public Comment

The IDN-Implementation Working Team has published the Final Report on three-character requirement and variant management for public comment. The public comment period ends on 8 January 2010.

The final report can be viewed at [PDF, 337K]. Comments can be submitted to, and viewed at

The Team was established to study two topics in anticipation of the delegation of Internationalized Domain Names (IDNs) into the root zone:

  • Management of variant Top-Level Domains (TLDs);
  • Whether there can be exceptions to the three-character requirement for generic Top-Level Domains (gTLDs).


Extensive community work has been conducted over the last few years on these two topics, including several proposals and public comment periods. Considering the breadth of discussion, it was determined at the ICANN Meeting in Sydney (June 09) to form an IDN-Implementation Working Team to assist in formulating implementation recommendations for variant management and the three-character requirement.

"Variant characters" are characters with two or more representations that may appear confusingly similar with each other. Variant TLDs contain one or more variant characters that can result in two domain names being visually confusing. As such, the resulting "variant strings" that are obtained by replacing the original characters with the variant characters might be visually indistinguishable and create user confusion.

For variants, the Team focused on:

  1. Developing a definition of variant TLDs;
  2. Determining whether blocking or reservation of variant TLDs is necessary to prevent user confusion;
  3. Determining under what circumstances TLD variants might be delegated, ensuring the user experience when using variant TLDs must be at least as good as when using TLDs without variants.

For the number of required characters in a gTLD string, the Team focused on: 

  1. Describing instances where users in certain language groups will be disadvantaged in ability to communicate/utilize the DNS due to the current three-character restrictions;
  2. Developing a clear set of rules for limited lifting of the three-character to alleviate the negative impacts described in the answer to the first question.

Summary of Recommendations

The Team made the following recommendations:

  1. Variant Management
    • TLD applicants (requesting a "base" label) may identify variant forms of that base label and classify each variant as 'desired' or 'undesired';
    • Desired variants can be allocated (i.e. reserved) to the applicant;
    • It is suggested that desired variants can be delegated to the applicant under specific circumstances and if the applicant agrees to conform to the rules described in the report;
    • Undesired variants will be reserved (i.e. blocked) and neither allocated nor delegated.
  2. Three-character Restriction in gTLDs
    • Two-character gTLD strings can be delegated subject to conformance to certain conditions outlined in the report;
    • The team does not recommend the banning of the one-character gTLDs. This issue is a matter of policy.

After the public comment period, a set of solutions will be devised for further discussion and consideration in the IDN ccTLD Fast Track Process, the IDN ccTLD PDP, and in the next version of the new gTLD Applicant Guidebook (New gTLD Program).

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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."