Punycode is a way to encode internationalized domain names (IDN) that contain non-ASCII characters into the ASCII subset supported by DNS. For example, "münchen.de" becomes "xn--mnchen-3ya.de". This tool uses the browser's native URL APIs for reliable encoding. Runs entirely in your browser.
Punycode is the bridge between human-readable Unicode domains (münchen.de, 例え.jp, 🍕.ws) and the ASCII-only world of DNS. This tool converts in both directions using the browser's native URL parser, which implements the IDNA 2008 / RFC 3492 algorithm — so the output matches what every modern browser actually resolves.
Encoding is per label: each dot-separated chunk is examined, and only those containing non-ASCII code points get the "xn--" prefix and ASCII-Compatible Encoding. Decoding reverses the process. Pure-ASCII labels pass through unchanged. The encoding is bit-exact and round-trippable, so any string you encode and then decode returns to its original form.
Punycode (RFC 3492) is the encoding that lets DNS — which only allows ASCII letters, digits, and hyphens — represent labels containing arbitrary Unicode. Each non-ASCII label is rewritten with the prefix "xn--" followed by an ASCII-Compatible Encoding of the original characters.
The "ü" cannot live in a DNS label, so it is moved to the end as a numeric reference (3ya) while the basic ASCII letters stay in place. The "xn--" prefix tells software the label is encoded and needs decoding before display.
Yes — emoji are just Unicode code points, so they encode the same way. ".ws", ".to", and a handful of other registries actually allow emoji second-level domains; most do not.
Lookalike Unicode characters (Cyrillic "а" vs Latin "a") can produce domains that read identically to a human but resolve to a different server — the so-called IDN homograph attack. Modern browsers display the raw "xn--" form for mixed-script domains to mitigate this.
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