Internationalized Domain Names (IDNs) under .de
Next to the letters a to z of the Latin alphabet, .de domains may also include special characters, such as the German umlauts. Domains the names of which comprise umlauts, other diacritics or letters from other alphabets than the Latin one are called Internationalized Domain Names (IDNs).
You can use a total of 93 additional special characters in the names of .de domains. You find them in the idn list. Permitting the characters of this list in .de domains, DENIC follows the revised standard for Internationalized Domain Names in Applications (also referred to as IDNA2008, see RFCs 5890 to 5894).
Our conversion routine allows you to see how an IDN is technically implemented by displaying the so-called ACE string.
Here is an example:
IDN version: überall-ist.de (.de is everywhere)
ACE string: xn--berall-ist-8db.de
Things to be Considered for Domains Containing the Letter Eszett (ß)
Previously, when a user entered a domain containing the Latin small letter sharp s, the web browsers automatically converted the "ß" into "ss". So domain names like "straße.de" automatically became "strasse.de". It depended on the browser type if this conversion was visible to the user in the address line. The present IDN standard, in contrast, stipulates that "ß" shall be a separate character and shall no longer be mapped to "ss". So "straße.de" and "strasse.de" now are two separate domains. As a result of the new rule, applications based on the former IDN standard are no longer compatible with the new standard. This is called lack of backwards compatibility.
As regards the user, the conversion may bring about unexpected results during a transition period because most web browsers and e-mail clients are still based on the old IDN standard. Thus, it depends on the software that is used, to which domains a user will be directed when entering a domain name that includes an "ß". While browser versions that are based on the new standard will display exactly the page the user has entered, older browser versions will always direct the user to the domain with “ss”. However, this domain may not necessarily be identical with the queried "ß"-domain, regardless whether both domains are registered by one and the same holder or not.
Therefore, DENIC recommends parties interested in ß-domains to take this technical uncertainty into consideration with regards to the use of the domain.