Why Domains Turn Into xn-- Strings
DNS carries only a restricted ASCII set, so an internationalized domain name is encoded label by label with Punycode, defined in RFC 3492, and each converted label is prefixed with xn--. The algorithm separates the ASCII characters from the rest and encodes the non-ASCII code points as a compact sequence of deltas, which is why münchen becomes xn--mnchen-3ya rather than something resembling percent-encoding. This converter implements the algorithm directly instead of relying on the browser URL parser, so it can show each label, whether it was encoded, and which scripts it mixes.
How to Convert a Domain
- 1Paste either form: a Unicode name such as münchen.de or an encoded one such as xn--mnchen-3ya.de. The direction is detected automatically.
- 2Read the two result panels to get the Unicode and ASCII forms, and copy whichever one your system needs.
- 3Check the label table to see which individual labels required encoding.
- 4Review any warning: mixed scripts within one label and labels that exceed the DNS length limits are both flagged.
- 5Use the ASCII form for DNS records, certificates and configuration files, and the Unicode form for display to people.
Where Punycode Comes Up
Read a suspicious link
Decode an xn-- host from an email or log entry to see the name a user would actually have seen in the address bar.
Configure DNS and certificates
Get the exact ASCII form required by zone files, TLS certificate subject names and server configuration.
Investigate homograph attacks
Spot a label that mixes Cyrillic or Greek characters with Latin ones, which is how lookalike domains are built.
Validate length limits before registering
Confirm that an encoded label stays within 63 characters and the whole name within 253.
Frequently asked questions
Why does the encoded name look nothing like the original?
Punycode is not a character-by-character substitution. It emits the ASCII characters first, then encodes the positions and values of the remaining code points as base-36 deltas. That produces a much shorter string than escaping each character, but it is not readable by eye.
Is a mixed-script warning proof that a domain is malicious?
No. Many legitimate names legitimately combine scripts, and Japanese in particular mixes Han, Hiragana and Katakana normally, which this tool does not flag. The warning marks a label worth reviewing, not a verdict.
Does this perform full IDNA processing?
It performs Punycode encoding and decoding per label and checks DNS length limits. It does not apply the complete IDNA2008 mapping and validity rules, so a registry may still reject a name this tool converts successfully.
Is the domain looked up or sent anywhere?
No. The conversion is pure arithmetic on the characters you type. No DNS query is performed and nothing leaves your browser, which matters when you are inspecting a hostname from a phishing message.