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Punycode Converter

Convert internationalized domain names (IDN) to Punycode and vice versa.

Updated

What is the Punycode Converter?

Punycode converts internationalized domain names (IDNs) with non-ASCII characters—such as Arabic, Chinese, Cyrillic, or accented Latin letters like ü, é, ñ—into the ASCII-compatible format required by the Domain Name System (DNS).

DNS only supports ASCII characters (A-Z, 0-9, and hyphens), so domain names containing other scripts must be encoded as Punycode to work on the internet. You can recognize Punycode domains by the xn-- prefix—for example, müller.com becomes xn--mller-kva.com.

This tool converts Unicode domain names to Punycode and back. It handles full URLs, email addresses, and batch processing, converting only the hostname or domain portion while leaving paths, protocols, and other parts unchanged.

How it works

This tool implements the Punycode algorithm (RFC 3492) to convert between Unicode domain names and their ASCII-compatible Punycode representations.

Encoding (Unicode to Punycode)

When you enter a Unicode domain name like müller.com:

  1. The tool identifies labels containing non-ASCII characters (e.g., müller). ASCII-only parts like .com stay unchanged.
  2. Each non-ASCII label is encoded using the Punycode algorithm, which represents Unicode characters as ASCII characters with the xn-- prefix. For example, müller becomes xn--mller-kva.
  3. The encoded labels are reassembled with the original ASCII parts to form the complete Punycode domain: xn--mller-kva.com.

Decoding (Punycode to Unicode)

When you enter a Punycode domain like xn--mller-kva.com:

  1. The tool identifies labels starting with xn-- (the Punycode prefix).
  2. Each encoded label is decoded back to its original Unicode characters.
  3. The decoded labels are combined with any ASCII-only parts to reconstruct the original domain: müller.com.

URL and Email Handling

The tool intelligently processes full URLs and email addresses by converting only the relevant parts:

  • URLs: Only the hostname is converted. For https://müller.com/path, the path remains unchanged in the output: https://xn--mller-kva.com/path.
  • Email addresses: Only the domain part is converted. For user@müller.com, the local part is preserved: user@xn--mller-kva.com.

Batch Processing

Enter multiple domain names, URLs, or email addresses (one per line) to convert them all at once. Each line is processed independently, maintaining the line-by-line structure.

Statistics

The tool shows real-time statistics including input and output character lengths, so you can see how Punycode encoding affects string size.

Examples

Convert Unicode domain to Punycode

Convert a domain name with special characters to its Punycode equivalent.

müller.com
 
xn--mller-kva.com

Convert Punycode domain to Unicode

Decode a Punycode domain back to its original Unicode form.

xn--mller-kva.com
 
müller.com

Convert a URL with Unicode characters

Encode a full URL containing internationalized characters.

https://www.bücher.de/shop
 
https://www.xn--bcher-kva.de/shop

Convert an email address with Unicode characters

Encode the domain part of an email address with special characters.

kontakt@müller.com
 
kontakt@xn--mller-kva.com

Batch conversion of multiple domains

Convert several Unicode domains at once, each on a new line.

example.com
müller.com
façade.org
 
example.com
xn--mller-kva.com
xn--faade-zra.org

Frequently asked questions

What is Punycode?

Punycode is an encoding that converts Unicode characters into ASCII, allowing internationalized domain names (IDNs) to work within the Domain Name System (DNS), which only supports ASCII characters.

Why is Punycode necessary?

DNS was designed to use only ASCII characters (A-Z, 0-9, and hyphens). Without Punycode, domain names containing characters from other languages—like é, ü, ñ, or Cyrillic, Arabic, or Chinese scripts—would not resolve on the internet. Punycode provides a standardized way to represent these international characters in an ASCII-compatible format.

How do I identify a Punycode domain?

Punycode domains start with the prefix xn--. For example, müller.com in Unicode becomes xn--mller-kva.com in Punycode.

Can Punycode be used for URLs and email addresses?

Yes, Punycode is used for the domain name portion of URLs and email addresses. This tool converts only the hostname or domain part, leaving protocols, paths, and other components unchanged. For example, https://müller.com/path becomes https://xn--mller-kva.com/path, and user@müller.com becomes user@xn--mller-kva.com.

Is Punycode secure? Can it be used for phishing?

Punycode itself is a standard encoding mechanism and is not inherently insecure. However, it can be exploited in phishing attacks called homograph attacks, where attackers register domains that look visually similar to legitimate ones using different Unicode characters (e.g., replacing Latin letters with visually similar Cyrillic ones). Modern browsers and email clients have protections to detect and warn about deceptive Punycode domains.

What is the difference between Punycode and IDN?

IDN (Internationalized Domain Name) refers to a domain name containing at least one non-ASCII character—these are the human-readable domain names in various languages. Punycode is the encoding mechanism that converts IDNs into the ASCII format that DNS can process. Put simply: IDN is the concept of a multilingual domain name, and Punycode is the technical encoding that makes it work.

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