Policy for IDN Code Points

The Verisign Shared Registration System (SRS) allows the creation of Internationalised Domain Names (IDNs) that contain Unicode supported non-ASCII scripts. Verisign has developed a policy for IDN registrations specifying permissible and prohibited code points.

Internet engineering task force (IETF) Standards

IDNA2008 Request for Comments (RFCs) specifies algorithms and rules that permit/prohibit Unicode points in IDN registrations. Verisign is in compliance with IDNA2008 RFCs. Please review the IETF Standards here. A complete list of Unicode points permissible for IDN registrations is here. A complete list of Unicode points permissible for IDN registrations is here.

Restrictions on Commingling of Scripts

The Unicode Standard defines a set of Unicode Scripts by assigning each Unicode data point exactly one Unicode Script value. As a rule, the .com, .net, .name, .tv and .cc registries reject the commingling of code points from different Unicode scripts. That is, if an IDN contains code points from two or more Unicode scripts, then that IDN registration is rejected. For example, a character from the Latin script cannot be used in the same IDN as any Cyrillic character. All code points within an IDN must come from the same Unicode script. This is done to prevent confusable code points from appearing in the same IDN. An exception to this rule is made for well-defined languages that want to allow this commingling in certain circumstances as discussed in the next section.

Restrictions on Specific Languages

When an IDN registration is requested, the language tag is checked against a list of languages that have character inclusion tables or character variant mapping tables. These tables are applied to the Unicode points that make up a registration to determine whether the registration is valid for a specific language. For a more detailed explanation of the relationship between scripts and languages, click here. The following table lists the languages that have language tables.

ICANN’s Restricted Unicode Points

The Verisign SRS also adheres to ICANN’s Guidelines for the Implementation of Internationalised Domain Names. Section 5 of the document outlines characters that are allowed by the IETF standard, but should be prohibited for IDN registration. For this reason, the Verisign SRS prohibits the following Unicode code points in all .com, .net, .name, .tv and .cc registrations. A complete list of ICANN’s restricted Unicode points is here.

Special Characters

There are exactly two (2) Unicode characters whose latest definitions are not backwards compatible with previous versions of the IDNA Standard. The Latin Sharp S and Greek Final Sigma were previously mapped to other characters. Clients and Registries compliant with the older standard would, for instance, map a Latin Sharp S into two lowercase Latin letter S characters. This mapping is irreversible. The latest version of the IDNA standard does not apply this mapping. So, whereas the Latin Sharp S was previously prohibited (mapped into other characters), the latest standard allows Registries to accept this character at their own discretion.

Because these changes are not backwards compatible, Verisign has elected to continue to disallow these two (2) characters, until a clear approach to their registration has been reached and communicated.

Chinese Character Variants

Certain characters in Chinese have the same meaning and pronunciation, but are visually different. These characters are called character variants. For a more detailed description of character variants click here. When a domain is registered with a Chinese character that has variants, then all other variants for that Chinese character will be prohibited from registration. For a list of Chinese characters with variants, click here.