Punycode Converter
Convert international domain names between Unicode and Punycode (xn--) format
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About Punycode Converter
Punycode Converter - Decode and Encode Internationalized Domain Names
The Punycode Converter translates between Unicode text and Punycode encoding, the system that makes internationalized domain names work on the internet. If you have ever seen a domain name starting with xn-- and wondered what it means, or if you need to register a domain using non-Latin characters, this tool decodes and encodes Punycode instantly in your browser.
Why Punycode Exists
The Domain Name System was designed in the 1980s when the internet was primarily an English-language network. DNS labels were restricted to ASCII letters, digits, and hyphens - a character set that works fine for English but excludes billions of people who write in Chinese, Arabic, Hindi, Cyrillic, and hundreds of other scripts. Punycode bridges this gap by providing a way to represent Unicode characters using only the limited ASCII character set that DNS supports.
When someone registers a domain with non-ASCII characters, the domain is actually stored in DNS with an xn-- prefix followed by the Punycode encoding. Your browser performs the conversion automatically, showing you the Unicode version in the address bar while communicating with DNS using the ASCII-compatible encoding. This system, formally called Internationalized Domain Names in Applications (IDNA), is defined in RFC 3492.
How Punycode Encoding Works
The Punycode algorithm is surprisingly sophisticated. Rather than using a simple lookup table, it employs a generalized variable-length integer encoding scheme called bootstring. The algorithm separates the input into basic ASCII characters (which pass through unchanged) and non-ASCII characters, then encodes the non-ASCII characters as a series of insertions specifying position and Unicode code point.
An adaptive bias mechanism adjusts based on the distribution of code points being encoded, resulting in very compact output. A domain name in Japanese or Arabic that might contain 10 Unicode characters encodes to a Punycode string typically only 15 to 25 ASCII characters long.
Using the Punycode Converter
The Punycode Converter works in both directions. To encode, type or paste Unicode text containing international characters and get the xn-- prefixed representation. To decode, paste a Punycode string and see the original Unicode text. The tool handles full domain names, converting each label independently as the standard requires.
Practical Applications
Web developers and domain administrators use the Punycode converter regularly. When configuring SSL certificates for internationalized domains, you often need the Punycode form. DNS zone files require Punycode for IDN entries. Email servers handling addresses at internationalized domains need both forms for different protocol stages.
Security researchers use Punycode tools to analyze homograph attacks, a type of phishing where an attacker registers a domain using characters from different scripts that visually resemble a legitimate domain. Understanding Punycode encoding is essential for detecting these attacks.
IDN Standards and Browser Behavior
Modern browsers handle Punycode with varying levels of sophistication. Most display the Unicode form in the address bar when the domain uses characters from a single script, but show the raw xn-- form when mixed scripts are detected as a defense against homograph attacks.
Free, Private, No Limits
The Punycode Converter runs entirely in your browser. Convert as many domain names as you need, in either direction, with no accounts required and complete privacy guaranteed.