Punycode Converter
Punycode Converter — runs in your browser. Inputs are not stored.
Punycode / domain conversion
Enter values, then press Calculate.
Normalizes the hostname with the browser URL API. Use it to convert IDN ↔ xn--.
How to use
- In domain, enter a Hangul or Unicode host or an
xn--ASCII domain.https://or a path may be attached. - Press Enter or Convert. Protocol, path, and port are discarded; only the host is used.
- ASCII / Punycode (hostname) shows the host normalized by the browser URL API. Internationalized domains usually have an
xn--prefix. - Unicode display keeps that host (lowercase) if the input has non-ASCII; otherwise it shows the ASCII host as-is.
- On parse failure, a note appears in the ASCII field. Reset clears it. No lookup or WHOIS request is made.
- When comparing cookie Domain or TLS certificate CN, copy the ASCII field and match it to server settings. No DNS lookup is sent.
Key concepts
Punycode is how internationalized domain names (IDN), including Hangul, are moved to the ASCII DNS handles. Even if the address bar shows a Hangul domain, the actual query goes to an xn-- prefix host. This tool uses no extra library: it shows the normalization your current browser applies via new URL('http://' + host).hostname. Scheme, path, and port are dropped from the input, leaving the host only.
When checking certificates, cookies, CORS, mail servers, or lookalike phishing domains, matching “the name on screen” with “ASCII on the wire” reduces mistakes. There is no DNS lookup or WHOIS. The Unicode field keeps the host only when the input has non-ASCII, so pasting xn-- alone may not restore Hangul automatically. Values stay in the browser only.
Example
Converting 한글.com puts a Punycode host of the form xn--bj0bj06e.com in the ASCII field and keeps the lowercase Hangul host in the Unicode field. https://한글.com/path:443 still uses the host only. English www.example.com looks similar on both sides after URL API normalization. When filling a mail server or certificate CN, copying the ASCII field is the safer habit.
Related: URL encoder · Character counter · Hash generator
Frequently asked questions
What is Punycode conversion?
It is the notation that represents an internationalized domain (IDN) as the ASCII DNS uses (<code>xn--</code> prefix). This page shows that result via the browser URL API’s hostname normalization.
How do I check the xn-- address of a Hangul domain?
Enter the Hangul host, press Convert, and copy the <code>xn--</code> value in the ASCII field. Use that value when matching certificates and name-server settings.
Does Punycode conversion work if I prepend http://?
Yes. <code>https://</code>, path, and port are stripped, then only the host is converted. Enter also runs it.
Does it turn xn-- back into Hangul?
If the input contains Hangul, the Unicode field keeps it in lowercase. If you paste ASCII (<code>xn--</code>) only, Hangul may not restore automatically.
Do subdomains and ports work?
The port number is stripped; host labels are handled by the URL API. An invalid host shows a parse-failure note in the ASCII field.
Does domain conversion send a DNS lookup?
No. It only normalizes the string. It does not send WHOIS or DNS queries or log the domain on a server.
Last reviewed: 2026-09-04