Internationalized Domain Names
What Internationalized Domain Names Are and Why They Exist
Internationalized domain names (IDNs) are domain names that contain characters beyond the basic Latin alphabet, such as accented letters like é or ü, or Cyrillic, Arabic and Chinese script. They let people write an address in the letters they use every day, rather than only in English-style spelling.
The original domain system was built around ASCII, a set of 128 characters covering the letters a to z, the digits 0 to 9 and the hyphen. IDNs were developed to remove that limit, so the name a person sees can be written in Unicode, the standard that assigns codes to characters in almost every writing system.
Behind the scenes, the internet still needs an ASCII form of each name to route traffic. A conversion step translates between the two forms. The mechanism is explained in Punycode.
Where IDNs Work Well and Where They Fall Short
IDN support has grown considerably. Modern browsers display IDNs in their native script, and most major websites work with them. Support is weaker in older software, in some mail systems and in applications that handle domain names as plain text.
Two practical limits matter most. First, each registry, the organisation that runs a top-level domain such as .com, sets its own list of permitted characters. A name in one script may be accepted under one extension and refused under another. Second, email addresses with non-ASCII characters need special support from mail servers, and many services still do not offer it.
Typing is a third issue. Visitors need a keyboard that can produce the right characters, which makes an IDN harder to share by word of mouth. A bakery in Munich might want an umlaut in its name, but customers who cannot type it may search for the plain version. Some owners therefore register an ASCII version alongside the IDN. Extensions are covered in what a top-level domain is.
Frequently asked questions
Are internationalized domain names safe to use?
Yes, IDNs are a standard, supported part of the domain system. The main concern is look-alike characters: some letters from other scripts appear identical to Latin letters, so a fake name can be made to resemble a familiar brand. Registries and browsers apply rules to reduce this risk, and the encoding behind it is the subject of a separate article on punycode.
Do IDNs work in email addresses?
Sometimes, but not reliably. Email needs its own support for non-ASCII characters in addresses, and many servers, apps and mailing lists do not offer it yet. A business with an IDN website often uses a plain ASCII address for email.
Can I use an IDN with any domain extension?
Not always. Each registry sets its own rules on which characters it accepts, based on the scripts used in its market and its policies. A character accepted under one extension may be refused under another, and some extensions only accept IDNs in particular languages.