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Internationalized Domain Name (IDN) SDKs

FreeYourID's IDN Software Development Kit (SDK) provides application developers with general purpose libraries that implement the latest Internationalized Domain Names in Applications (IDNA) standards. The IDN SDK supports Domain Registrars in the process of normalizing and encoding data for DNS registration. However the library provides tools for any client or server applications that may need to convert from one encoding to another.

IDN Standards

The FreeYourID implementation of IDN registration for the .com, .net, .tv, and .cc top-level domains (TLDs) follows the specification set forth by the Internet Engineering Task Force (IETF) in these RFC documents:

  • RFC 3490 - Processes for Punycode
  • RFC 5891 – IDNA Protocol
  • RFC 5892 – IDNA Unicode
  • RFC 5893 – IDNA Right-to-Left Scripts
  • RFC 5894 – Rationale
  • RFC 5895 – Character Mapping


The latest version of FreeYourID's IDN SDK includes a User's Guide, a Programmer's Guide, and a Registrar's Guide. The User's Guide provides a high-level look at the contents of the library and an overview of the problems that it can solve. The Programmer's Guide contains instructions for users who will incorporate or extend the software provided in the library. The Registrar's Guide gives instructions on how to create Punycode domains and also provides some help in troubleshooting common errors during registration.

Download the IDN SDK

The library is delivered in the ZIP file format. The data inside is compressed and archived. Most operating systems can natively decompress this format. Various third-party tools are also available.

The single IDN SDK package (~5 MB) contains all software, including an API, tools, and tests for both C and Java languages.

Additional IDNA Libraries

Libraries that implement the IDNA standard for a variety of programming environments are available in the public domain. FreeYourID encourages and supports the work of such developers and provides links to these libraries. Application developers should choose the library that best fits their application requirements.

If you are a reseller, please contact your registrar partner for more information on these services.

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