What is the ACE format?

The ACE format is the ASCII representation (without diacritics) of domain names that contain diacritics or other special characters. This representation allows DNS systems to work with these special domains.

A domain name in ACE format starts with the characters xn--, indicating that it is an internationalized domain (containing diacritics).

For example, the domain name românia.ro corresponds to xn--romnia-yta.ro in ACE format.

When registering a domain name with diacritics, you can use either the IDN format (with diacritics) or the ACE format.