Comment en Coder Punycode Domains
Convertir internationalized domain names (IDN) to Punycode ASCII representation for DNS resolution.
问题
You avoir un domain nom avec non-ASCII caractères (e.g., Bücher.com) et besoin its Punycode form pour DNS lookups.
Prérequis
- Understanding of DNS
- Familiarity with Unicode
Étapes
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1. Split the domain into labels
Separate the domain name at each dot. Punycode is applied per-label, not to the whole domain. The TLD and each subdomain label are processed independently.
entréeBücher.com输出labels: ['Bücher', 'com'] -
2. Encode each non-ASCII label to Punycode
For each label containing non-ASCII characters, prefix the Punycode output with xn-- and append the encoded form. ASCII-only labels like 'com' remain unchanged. The encoding maps Unicode code points to a compact ASCII representation.
entréeBücher输出xn--Bcher-kva -
3. Reassemble and verify
Join the encoded labels with dots. Use the result for DNS resolution. Most browsers and DNS libraries perform this conversion automatically, but APIs and logs often show the Punycode form.
entréexn--Bcher-kva.com输出resolves to the same server as Bücher.com
Résultat attendu
Un ASCII-seulement domain nom (ACE form) ce DNS resolvers peut requête, equivalent en le original IDN.
Erreurs courantes
- Encoding the entire domain as one label
- Split on dots first. Only labels with non-ASCII characters get the xn-- prefix.
- Case is lost in conversion
- Punycode preserves the case of the first character. Use a standards-compliant encoder to handle case correctly.
Dépannage指引
- If DNS lookup fails, verify the xn-- prefix is present and lowercase.
- Some older resolvers do not support IDN. Use the Punycode form directly in those cases.
Limites de sécurité
- Punycode enables homograph attacks (e.g., аpple.com using Cyrillic а). Always display the Unicode form to users and warn about mixed-script domains.