Punycode and IDN Converter

Domain names can contain non-English letters, for example münchen.de. DNS only understands ASCII, so these names are stored in Punycode, such as xn--mnchen-3ya.de.

This tool converts in both directions. You can paste bare domains or full URLs. Only the domain part is converted, and the rest of the URL is left unchanged.

Key features

• Unicode to Punycode (xn--)
• Punycode to Unicode
• Accepts domains or full URLs
• One per line for bulk conversion

Example

münchen.de  =  xn--mnchen-3ya.de

How to use

1. Paste your domains or URLs.
2. Click To Punycode or To Unicode.
3. Copy the result.

Use cases

• Setting up DNS or SSL for an internationalized domain
• Reading xn-- domains in logs and reports
• Checking suspicious look-alike domains

In depth

Punycode, defined in RFC 3492, is the encoding behind internationalized domain names. DNS labels are limited to ASCII letters, digits and hyphens, so each non-ASCII label is converted separately. The algorithm copies the ASCII characters first, then encodes the positions and values of the remaining characters as a compact sequence of base-36 digits, and the label is prefixed with xn-- to flag it. In the name muenchen written with an umlaut, the ASCII letters stay readable and the umlaut is stored in the encoded tail after the final hyphen.

The conversion here works label by label, so only the parts of the domain between dots that contain non-ASCII characters are encoded. Before encoding, text is normalized to Unicode NFC form and lowercased, which mirrors part of the IDNA processing browsers do. Full IDNA 2008 rules, defined in RFC 5890 onward, add more validation, such as rejecting some characters. Look-alike characters from different scripts can imitate familiar names, so checking the Punycode form is a useful defence against phishing.

Tips

• Paste full URLs when you want the rest to stay untouched. Only the host part is converted, so the path and query string are kept exactly as typed.
• Use the Punycode form when entering an international domain into DNS, certificate requests or server configuration. Many control panels and tools expect the ASCII xn-- version.
• Inspect unfamiliar xn-- domains by converting them to Unicode before clicking. Characters from other scripts can look identical to Latin letters, so the decoded form can reveal a spoof.

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