An IDN (internationalised domain name) is a domain that contains non-ASCII characters, such as accented letters or non-Latin scripts.
An IDN lets people use domain names in their own language and alphabet. Originally, domains could only contain the English letters a to z, digits and hyphens. IDNs allow characters such as é, ü, ß, Chinese, Arabic, Cyrillic or Hindi script, so a café in Paris can register café.fr and a business in Russia can use a name written in Cyrillic.
There are also IDN extensions, so the whole address can be in another script. For example, .рф is the Cyrillic country code for Russia and .中国 is China's.
How IDNs work
The DNS itself still only understands basic ASCII characters. To make IDNs work, the name is converted into an ASCII form called Punycode before it's looked up. Every converted label starts with xn--.
For example, münchen.de becomes xn--mnchen-3ya.de behind the scenes. Browsers do the conversion automatically, so visitors type and see the readable version. Your DNS records, SSL certificate and server configuration may show the Punycode version instead.
Why IDNs matter
- Local audiences: people can type and remember a name in their own language.
- Brand accuracy: a business called Müller can use the real spelling instead of
muellerormuller. - Availability: an accented or non-Latin version of a name may be free when the plain one is taken.
Common IDN problems
- Typing difficulty: visitors without the right keyboard may struggle to enter the address, so many owners also register the plain ASCII version and redirect it.
- Email support: IDN email addresses aren't supported everywhere, and some forms reject them.
- Software support: older plugins, analytics tools or control panels may show or require the
xn--version. - Lookalike attacks: some characters from different scripts look identical, such as the Latin "a" and the Cyrillic "а". Scammers use this to create fake domains that look like real brands, a trick known as a homograph attack. To counter this, browsers may show the Punycode form when a name mixes scripts in a suspicious way.
Can I register an IDN?
Usually, yes. Many gTLDs and ccTLDs accept IDNs, but each registry decides which languages and characters it allows. When you register, you may be asked to choose the language of the name. Check the rules for your extension, and think about also registering the closest ASCII spelling to protect against typosquatting.