@hackage / idna2008

A Haskell library for parsing and validating internationalized domain names, which may contain characters from non-Latin scripts (Greek, Hebrew, Arabic, CJK, ...) alongside the conventional letters, digits, and hyphens. . Given a domain name as the user typed it, the library checks that every label is well-formed, encodes any non-ASCII labels into their ACE-prefixed form for the wire, tells the caller what kind of label each one is, and (optionally) renders the parsed name back to display form. . A single domain name often mixes several kinds of labels. The library reports each label as one of: a conventional hostname-style letter-digit-hyphen label, a legacy reserved label, an internationalized label encoded as Punycode, an "xn--"-prefix that turns out not to decode cleanly, a Unicode label, an underscore-prefixed service-discovery label (e.g. _25._tcp, _dmarc), an arbitrary-bytes label, or the DNS wildcard. Most existing IDNA libraries don't make these distinctions; this library does. . Strict IDNA2008. Some browsers and language standard libraries use a more permissive variant of the IDNA standard that accepts characters strict IDNA2008 rejects; this library does not use that variant. . Originally factored out of the dnsbase library; conformance test vectors are published as JSON for reuse by ports to other languages.