Punycode Converter

Domain names can only officially contain ASCII letters, digits, and hyphens, but people need domains in every script and language. Punycode is the encoding (defined in RFC 3492) that represents any Unicode text as an ASCII string prefixed with xn--, so a domain like münchen.de becomes xn--mnchen-3ya.de under the hood while browsers still display the Unicode version to users.

Domain name mode matches what actually happens on the internet: it splits on dots, leaves plain ASCII labels alone, and adds or removes the xn-- prefix only on labels that need it, so a full hostname like café.example.com converts correctly label by label. Plain text label mode runs the raw Punycode algorithm on the exact string you give it with no dot-splitting and no xn-- prefix, useful if you already have a bare encoded label from another tool or an RFC 3492 test vector.

Punycode decoding only succeeds on a well-formed encoded string; a line that is not valid Punycode, or a domain mode line whose label does not actually start with xn--, cannot be decoded and that line is reported as an error while the rest of the input still converts normally.

Yes, put each domain or label on its own line; the output textarea mirrors the input line by line, so line 3 of the output is always the conversion of line 3 of the input.

Yes, this tool uses the widely used punycode.js library (the modern successor to the Punycode implementation that shipped in Node.js itself for years), implementing the Bootstring algorithm from RFC 3492 exactly, the same specification every major browser follows when it shows a Unicode domain in the address bar.