Internationalised Domain Names (IDNs) is the term used for Internet domain names written using local languages and scripts. All characters which are not one of the 26 letters of the English alphabet, the numbers 0-9 or a hyphen (minus sign) are treated as IDN characters. Thus every domain name which contains at least one IDN character is referred to as an IDN.
The Swedish å, the German ü, the Romanian ş, the letters of the Russian or Greek alphabet, and of course all the letters of the Serbian Cyrillic script, are all examples of IDN characters. All the characters which can be used in IDNs are defined by the Unicode tables for the different scripts. IDNs may contain all of these special characters (for example: bücher.eu, åsen.no, рнидс.срб).
On this page you can see how a Unicode IDN looks when converted into an ACE (ASCII Compatible Encoding) string, also known as PUNICODE. The ACE form of internationalised domain names allows the DNS to resolve a Unicode domain name and link it with the corresponding address on the Internet.
The ACE string of characters begins with the four-character string “xn--” which marks the domain as an IDN. The remaining characters of the ACE domain name use a combination of ASCII characters to represent the Unicode characters which make up the internationalised domain name. One Unicode character is typically represented by a combination of two ASCII characters.
For example, the domain name тест.срб (test.srb) in ACE form is “xn--e1aybc.xn--90a3ac”.
The tools you use to browse the Internet must be IDN domain name-ready. The ACE string of characters is obtained when the IDN, which you type in your Internet browser’s address field, is converted into the form understood by the DNS.
Unicode domain name:
ACE domain name: