IDN abbreviation stands for Internationalized Domain Name. IDN defines a domain name containing national diacritical characters specific for particular language, that contains non-ASCII characters. , for example: ą, ć, ę, ł, ń, ó, ś, ż, ź (Polish diacritics).

IDN list of characters available for registration of .EU domain names is available on the Supported Unicode characters in EURid.

More information about the .eu domain names with national characters can be found on IDNs for .eu in EURid.