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IDN domain – Frequently asked questions

Q: What does IDN stand for?

  • A: IDN (Internationalized Domain Name) is a domain name made up of characters outside of the ASCII (American Standard Code for Information Interchange) system. For example, õ, ä, ö and ü used in Estonian language are characters outside of the ASCII system. So are the Swedish å, Romanian ș, the Greek alphabet and the Cyrillic alphabet.

Q: Can I register the domain PÕÕSAS.EU?

  • A: Yes. IDN names are now allowed in the EU and EE domains, which allows you to register a domain name with any dotted letters.

Q: Which characters are allowed in IDN domain names?

  • A: The list of characters allowed in IDN names can be found here.

Q: Why does my browser show a domain containing dotted letters as something else?

  • A: The reason is that the Domain Name System (DNS) used on the Internet only recognizes standard ASCII characters. In order for a domain with dotted letters to work it’s automatically converted to a format that the DNS can read. This format is called ACE string (ASCII Compatible Encoding). In order to recognise an IDN domain, the ACE string starts with four characters: XN–. Other characters in the domain name indicate which characters entered are outside the ASCII character system and where they are located. For example, the ACE string for the domain name PÜHVEL.EU is XN-PHVEL-KVA.EU.

Q: How long can an IDN domain name be?

  • A: The maximum length of IDN domain names is 63 characters. That limit is used after domain is translated to ACE string. For example, ABCDEF.EU is six characters long, XYZ.EU is three characters long, and PÜHVEL.EU is already 13 characters because after conversion the domain name looks like this: XN-PHVEL-KVA.EU
    Although the conversion results in a domain name Ä.EU with an ACE string of seven characters, it is still not possible to register it because the EU domain name must be at least two letters long. A good tool to find out the ACE string of a domain containing characters can be found here.

Q: Is there a distinction between upper and lower case letters in a domain name?

  • A: No. There is no difference between uppercase and lowercase letters in a domain name.

Q: Are there any additional conditions for registering an EU domain with dotted letters?

  • A: No. There are no additional requirements for registering an EU domain with a dot domain. There is no sunrise period for the registration of IDN domain names for EU domains.

Q: Can my web browser and email client understand punctuation?

  • A: Yes, most modern web browsers can understand IDN domain names. Please note however that many other applications may not support the IDN system. For example, if you have registered a domain with dotted characters in it and have set up an email associated with it in order for emails to reach you the email associated with the IDN domain must be introduced to other users via the ACE string. For example email address INFO@PÜHVEL.EU address would be INFO@XN-PHVEL-KVA.EU.

Q: Can I mix different alphabets in the IDN domain?

  • A: No. This is primarily to avoid the use of homoglyphs in the domain name. homoglyphs are characters from different alphabetic systems that appear identical to the eye, but have different UNICODE numbers. For example, the Cyrillic “а” and the Latin “a” are apparently identical, but their UNICODE numbers are 0430 and 0061 respectively. Therefore, to avoid confusion and legal disputes, different alphabets cannot be used in the same IDN domain name.
Updated on 22. May 2024

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