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1 Introduction

Libidn2 is a free software implementation of IDNA2008, Punycode and Unicode TR46. Its purpose is to encode and decode internationalized domain names.

The library is a rewrite of the popular but legacy libidn library, and is backwards (API) compatible with it. See Converting from libidn for more information.

For technical reference, see:

• IDNA2008 Framework (https://tools.ietf.org/html/rfc5890)
• IDNA2008 Protocol (https://tools.ietf.org/html/rfc5891)
• IDNA2008 Unicode tables (https://tools.ietf.org/html/rfc5892)
• IDNA2008 Bidi rule (https://tools.ietf.org/html/rfc5893)
• Punycode (https://tools.ietf.org/html/rfc3492)
• Unicode IDNA Compatibility Processing (http://www.unicode.org/reports/tr46/)

Libidn2 uses GNU libunistring (https://www.gnu.org/software/libunistring/) for Unicode processing and optionally GNU libiconv (https://www.gnu.org/software/libiconv/) for character set conversion.

The library is dual-licensed under LGPLv3 or GPLv2, see the file COPYING for detailed information.