IDN Punycode Converter

About IDN Punycode converter

This converter turns an internationalized domain name, such as münchen.de, into its Punycode form xn--mnchen-3ya.de and back again. It shows each dot-separated label in a table, marks which ones changed, and warns when a label mixes writing systems in the way look-alike phishing domains often do. Web developers, DNS admins and security teams use it to see the name a resolver actually receives.

How to use it

1. Choose a direction with the toggle: Unicode → ASCII to encode, or ASCII → Unicode to decode.
2. Type the domain into the input box, or click one of the sample domains underneath it.
3. Read the converted name in the Result box and check the Label breakdown table for what happened to each label.
4. Click Copy, or use Swap direction to feed the result back in and confirm the round trip.

Encoding a German domain

münchen.de

xn--mnchen-3ya.de

When to use it

• Finding the exact ASCII hostname to put in a DNS record, certificate request or server config for a non-English domain.
• Decoding a suspicious xn-- address from an email to see the characters it really contains.
• Checking that a domain you registered round-trips correctly before you print it on marketing material.
• Teaching or debugging the RFC 3492 encoding by watching how each label is converted independently.

Questions about IDN Punycode converter

What does the xn-- prefix mean?

It marks a label that holds Punycode, the ASCII-safe encoding of Unicode characters. Any label with characters outside ASCII gets that prefix when encoded, while plain ASCII labels are left exactly as they are.

What does the Possible look-alike domain warning mean?

A single label contains letters from more than one script, such as Latin mixed with Cyrillic. That is a common phishing trick. It is a basic check only, not a full confusable analysis, so treat it as a hint rather than proof.

Why might my browser show a different result?

This tool applies the raw RFC 3492 algorithm and keeps letter case. Browsers also lowercase and normalize names under IDNA rules first, so München.DE encodes here with its capitals kept, and the tool notes any difference.

What input does it reject?

It wants a bare domain. Anything containing a scheme, path, spaces, an at sign or an empty label, such as two dots in a row, produces an error rather than a guess.

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