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Umlaut domain

What is an umlaut domain?

An umlaut domain is an Internet address that, in addition to letters of the Latin alphabet and numbers, may also contain special characters, for example the German umlauts ä, ö and ü, the letter ß and other characters. Umlaut domains are therefore also called special character domains or IDN. The abbreviation stands for the English term internationalized domain name. Since the use of an umlaut domain is associated with disadvantages with regard to the range through a limited circle of users and technical difficulties can occur, their distribution is low. IDN domains account for only around 4 % of all registered domains.

Registry decides on permissible characters

In principle, almost all characters from the standardized Unicode character set are also possible in an umlaut domain. A list of IDN-compatible characters is available at

However, this does not mean that all characters may also be used with every domain extension, the so-called top-level domain. This is decided by the respective registry. For .de domains, it is DENIC.

According to the IDN character list of DENIC, 93 special characters are allowed. There are separate registries for the new top-level domains, for example dotBerlin for .berlin. They have their own, often more restricted sets of rules.

Use with risks

When using umlaut domains, especially in the commercial sector, it is necessary to weigh up the technical disadvantages and the advantages in terms of availability and readability.

A significant advantage of umlaut domains is that at the start of registration – for .de domains on 1 March 2004 – there were still many sought-after names available. By the way, ö was sold first, which is currently forwarded to another umlaut domain, sä

Another reason is the better readability. Bäckerei Müller simply looks more familiar than Baeckerei Mueller, and Suessoelgefaess, if the word exists at all, is hardly recognizable after dissolving the umlauts and the ligature ß. However, the familiar appearance of the name is over when umlaut domains are converted into a format suitable for the Internet.

With the help of a converter, such as the one provided by DENIC, you can check what becomes of an IDN domain if you translate it into a so-called ASCII-compatible string (ACE string, ACE = ASCII Compatible Encoding).

The handy address bäckerei-mü then becomes And that is really no longer self-speaking. However, such a translation of umlaut domains is necessary, for example so that links work. If this were not the case, backlinks would possibly be lost or the content would not be shared as frequently in social media. Both of these have a negative impact on search engine rankings. Technical difficulties are not excluded despite the conversion, because some browsers resolve umlauts or the ß directly when typing in ae, oe, ue or ss. Wrong page impressions are preprogrammed: and neustraß lead to completely different websites.

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