Encoding · Domains
Punycode & IDN converter.
Convert an internationalised domain name to its xn-- form, or decode one back, one label at a time. Runs in your browser; nothing is sent anywhere.
Input
Result
Enter a domain name and press Convert.
How the conversion works
Per label: a name is split at its dots and each label is converted on its own. A label that has any non-ASCII character is normalised (NFC), lowercased, encoded with the RFC 3492 Punycode algorithm and given the xn-- prefix. An all-ASCII label is left as it is (lowercased). bücher becomes xn--bcher-kva.
Length: each ASCII label may be at most 63 characters (RFC 5891, RFC 1035 section 2.3.4). Emoji and long scripts reach that limit sooner than you might expect.
Dots: the ideographic full stop (U+3002), fullwidth full stop (U+FF0E) and halfwidth ideographic full stop (U+FF61) are treated as label separators, as browsers do.
IDNA2008 and UTS #46 are not the same
IDNA2008 (RFC 5891) is strict: it decides which code points a label may contain and does not map anything, so an uppercase letter or a compatibility character is simply invalid. UTS #46 is the compatibility processing browsers use; it first maps such characters to a valid form and, in its transitional mode, treats a few characters differently from IDNA2008 (the German sharp s is the usual example). The same typed name can therefore give a different xn-- result in a browser than under a strict registry rule.
This tool applies the Punycode algorithm and simple NFC and lowercase folding. It does not carry the IDNA2008 code point tables or the UTS #46 mapping table. The result panel also shows what your own browser produces for the same name, so a difference is visible.
Homograph warning
A label that mixes scripts, such as a Cyrillic а inside otherwise Latin letters, can look identical to a different name. The tool flags a label that mixes scripts, except the usual Han, Hiragana, Katakana and Hangul combinations used in Japanese and Korean. A label written entirely in one script can still be a lookalike of another (whole-script confusable); detecting that needs the UTS #39 confusables data, which this tool does not include, so no warning does not mean safe.
Sources: RFC 3492 (Punycode); RFC 5891 (IDNA2008 protocol); Unicode UTS #46; Unicode UTS #39 (mixed-script detection).
Frequently asked questions
What is Punycode?
A way to write any Unicode string using only letters, digits and hyphens (RFC 3492). Domain names use it, with an xn-- prefix, so international names fit the ASCII-only DNS.
Is the converted name registered or safe to visit?
No. This converts text only. It does not check DNS, registry policy or whether a name is malicious.
Why does my browser show a different result?
Browsers apply UTS #46 mapping before encoding. Characters such as uppercase letters or compatibility forms may be mapped, so the output can differ from a plain Punycode conversion. Both results are shown.
Can I check the converted name afterwards?
Yes. Paste the ASCII result into the Hostname & FQDN Validator to check its label and length rules.
Conversion only
This tool converts and warns; it does not confirm that a name is valid under IDNA2008, allowed by a registry, registered, or free of lookalike risk.