Introduction GNU Libidn is a fully documented implementation of the Stringprep, Punycode and IDNA 2003 specifications. Libidn's purpose is to encode and decode internationalized domain names. The native C, C# and Java libraries are available under the GNU Lesser General Public License version 2.1 or later. Please be aware that GNU libidn2 is the successor of GNU libidn. It comes with IDNA 2008 and