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About Reserved Names

All registry operators are required by their Registry Agreement to exclude certain domain names from registration in a Top Level Domain (TLD). These reserved names include strings that are for Country Code Top Level Domains (ccTLDs), ICANN-related names (such as ICANN), IANA-related names (such as example), and names that the registry operator can use in connection with the operation of the TLD.

A list of reserved names for a registry operator of a TLD in which delegation of second level domain names began before the year 2013 is in Appendix 6 of its Registry Agreement, and in Specification 5 for a registry operator of a TLD in which delegation of second level domain names began during or after the year 2013. ICANN maintains a webpage with all current registry agreements.

ICANN is working with the community to develop a Name Collision Occurrence Management Framework that will be applied to all TLDs delegated into the root zone on and after 2013, which will produce an individual assessment per TLD indicating the mitigating measures that must be applied by the registry. In the interim, such TLDs may choose to proceed to delegation in advance of the forthcoming collision occurrence management by blocking all of the second level domains (SLD) identified in its alternate path to delegation report, if the TLD was found eligible for this measure. The list of SLDs that may be blocked per TLD is available as part of the documents associated with the TLD's registry agreement.

If you have a complaint about reserved names or a blocked SLD, please submit a Reserved and Blocked Second Level Domain (SLD) Names Complaint Form.

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""icann.org"" is not an IDN."