Internationalised Domain Names (IDNs)

IDN Rules

To be successfully registered, an IDN domain name must obey the following rules:

  • the "A-label" must be valid according to the IDNA2008 rules. We will test this by decoding the A-label to a UTF-8 string, and then re-encoding. If the re-encoded string matches the original string, this test is passed.
  • the "U-label" must contain at least the minimum number of characters. The minimum number varies depending on the domain extension and the registrar, but is normally 3.
  • the A-label must be a valid domain name in its own right (i.e. length and composition rules for ASCII domain names must also sucessfully be passed).
  • the U-label must not contain more than the maximum number of characters. This is 63 characters but may vary depending on the domain extension and the registrar.
  • the U-label must be wholly composed of characters from one of the IDN tables associated with the domain extension.

The IDN system allows Internet users to use the full alphabet of their language in their domain names. They're not restricted to the English A-Z, and can use the full latin character set, as well as characters from other locales, including Chinese and Japanese.

Internationalised (IDN) Domain Names work by encoding the domain name using a system called Punycode. When you wish to register an IDN domain, you must convert the domain name to Punycode, and register the encoded version of the domain name. Then when the user enters a URL containing an IDN domain into their web browser, it will convert the IDN domain into Punycode and resolve that domain.

For example, the IDN domain café.uk.com will convert into xn--caf-dma.uk.com which will be the version you register.

To avoid confusion and prevent fraud, IDN domain names may only be composed of characters from a limited subset of a given language or script. This is to prevent "homograph" attacks and other security problems, as well as to resolve issues relating to character variants within and between writing systems.

Each domain extension in our registry is associated with one or more IDN tables. A given IDN domain name may be registered only if all the characters it contains are members of one of these tables. There may also be additional contextual rules: please consult the policy associated with the IDN table in question for further details.

To view the IDN tables currently supported for our domain extensions, please go to the IDN Tables page.