Most domain names contain only the characters a-z, 0-9 and hyphens, but what do you do if your company is called “Björns Åkeri” or "Guðrún's Icelandic horses"? With the help of IDN, Internationalized Domain Names, you can use an increased number of characters in addition to character set that you were limited to.
Many people want to be able to express their identity or brand with their own language on the Internet, and a website can feel more consistent if the domain name is written in the same language as the content of the page.
Before year 2003, the Domain Name System (DNS), only allowed the characters a-z, digits 0-9 and hyphen in domain names, but with the help of the extension IDN, Internationalized Domain Names, you can use other characters in the domain name. IDN opens for large set of characters from the so called Unicode. Unicode is a character set that in principle contains all characters needed to write all languages in the world plus other characters and symbols that do not fit to be included in domain names, such as mathematically symbols and emojis.
IDN support at .se and .nu
For each top domain, for example .se, .com and .nu, it is decided if the IDN extension is to be done and if so what characters to permit.
For .se the list of included characters has been extended with å, ä, ö, ü and é, the characters used in the other Nordic languages, and all the characters in the official Swedish minority languages: Finnish, Meänkieli (Tornedals Finnish), Sami, Romani and Yiddish. A complete list of all the characters that can be used in .se domain names can be found in this character table.
For .nu the list has been extended with å, ä, ö, ü and é, as well as a large number of characters used for writing West European languages and the languages in the Nordic countries. A complete list of all the characters that can be used in .nu domains can be found in this character table.
Encoding IDN domain names
IDN is not just simple. When an IDN domain name is to be used in the DNS system it must be encoded using a special formula so that all characters except a-z, 0-9 and hyphen is converted to exactly a-z, 0-9 and bindestreck (we will not go into the details here). The IDN domain name räksmörgås.se becomes xn--rksmrgs-5wao1o.se but that is something that preferably should not be showned. When everything works as it should only IT people will need to see the encoded version, but unfortunately it pops up once in a while. It is good to know that if a domain name starts with xn-- it is an IDN domain name that has not been completely handled. It is possible to use the encoded version in the web browser, for example xn--rksmrgs-5wao1o.se, but that is something that should be avoided.
When you register an IDN domain name you do not have to think about encoding, because it is handled by the system, but you will see the encoded version if you search for your domain name in the Swedish Internet Foundation’s register of .se and .nu domain names.
So far, not all The Swedish Internet Foundation’s resellers (registrars) have support for IDN. To find out who supports IDN, you can filter the list by checking “Offers IDN domain name registration”.
Varied software support for IDN
All common web browsers have support for IDN unless you do not use a very old version, so you should not be too worried to loose visitors to your web site if you use an IDN domain name. In contrast, the support in mail clients is more limited. Other applications can also have limited support, but as a work-around you can use the encoded version.
Our recommendation is that anyone who wants to register an IDN domain should also have an ordinary domain name as a complement. It is not enough that the application, for example web browser, must support IDN domain names. If you want to type it in, for example from printed material, then you must have a keyboard with support for the same character set. On the other hand, you can always click on a link on a web site even if you cannot write the same string from the key board.
Coming so for about IDN domain names, we also want to tell you that there are top level domains, equivalent of .se and .nu, that are IDN domain names. Today there are, among others, top domain names with Chinese characters or Arabic characters.