What Is an Internationalized Domain Name?

How non-Latin scripts work in the DNS, what punycode is, and why it matters.

The problem

The DNS was designed for ASCII (A–Z, 0–9, hyphen). But the world writes in Arabic, Chinese, Cyrillic, Devanagari, Hebrew, Korean, and hundreds of other scripts. IDNs solve this.

How IDNs work: punycode

The DNS still only understands ASCII. IDNs use a standard encoding called punycode (RFC 3492) to represent Unicode labels as ASCII.

Example: 例子.测试 (Chinese for "example.test") becomes:

xn--fsqu00a.xn--0zwm56d

The xn-- prefix signals "this is punycode". The rest is the encoded form.

Two types of IDNs

TypeExampleNotes
IDN TLD (top-level).中国 (.xn--fiqs8s), .рф (.xn--p1ai)Delegated in the root zone like any TLD.
IDN second-level例子.com (xn--fsqu00a.com)Registered under an ASCII TLD; supported by most registries.

IDN TLDs in the root zone

As of 2026, there are over 150 IDN TLDs delegated. They include:

  • .中国 / .cn (China)
  • .рф (Russia)
  • .السعودية (Saudi Arabia)
  • .भारत (India)
  • .台湾 / .台灣 (Taiwan)
  • .한국 (Korea)
  • .香港 (Hong Kong)

Browse all of them in our IDN category.

Registration considerations

  • Not all registrars support IDNs — check before buying.
  • Email support varies — SMTP UTF-8 (RFC 6531) is required for email addresses with Unicode. Many providers still don't support it fully.
  • SSL/TLS certificates — modern CAs support IDNs, but you may need to specify the punycode form in CSR.
  • Browser display — modern browsers show the Unicode form in the address bar, but may show punycode for security (homograph protection).

Homograph attacks

Characters from different scripts can look identical (e.g. Latin a vs Cyrillic а). Attackers register lookalike domains for phishing.

Defences:

  • Browsers show punycode for mixed-script domains.
  • Registries apply script-mixing rules (e.g. .com allows Latin + Cyrillic but not Latin + Greek in one label).
  • Always verify the punycode form (xn--...) for important transactions.

Practical tips

  • If your audience uses a non-Latin script, an IDN TLD or second-level domain builds trust.
  • Always also register the ASCII transliteration if possible (e.g. register both 例子.com and lizi.com).
  • Test email delivery thoroughly before relying on an IDN email address.
  • Use our directory to find IDN TLDs — filter by "IDN only".