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idna 2.1

Internationalized Domain Names in Applications (IDNA)

A library to support the Internationalised Domain Names in Applications (IDNA) protocol as specified in RFC 5891. This version of the protocol is often referred to as “IDNA2008”.

This library also provides support for Unicode Technical Standard 46, Unicode IDNA Compatibility Processing.

The library is also intended to act as a suitable replacement for the “encodings.idna” module that comes with the Python standard library but currently only supports the older, deprecated IDNA specification (RFC 3490).

Its basic functions are simply executed:

>>> import idna
>>> idna.encode(u'ドメイン.テスト')
>>> print idna.decode('xn--eckwd4c7c.xn--zckzah')


The latest tagged release version is published in the PyPI repository:


To install this library, you can use PIP:

$ pip install idna

Alternatively, you can install the package using the bundled setup script:

$ python install

This library should work with Python 2.7, and Python 3.3 or later.


For typical usage, the encode and decode functions will take a domain name argument and perform a conversion to an A-label or U-label respectively.

>>> import idna
>>> idna.encode(u'ドメイン.テスト')
>>> print idna.decode('xn--eckwd4c7c.xn--zckzah')

You may use the codec encoding and decoding methods using the idna.codec module.

>>> import idna.codec
>>> print u'домена.испытание'.encode('idna')
>>> print 'xn--80ahd1agd.xn--80akhbyknj4f'.decode('idna')

Conversions can be applied at a per-label basis using the ulabel or alabel functions if necessary:

>>> idna.alabel(u'测试')

Compatibility Mapping (UTS #46)

As described in RFC 5895, the IDNA specification no longer including mappings from different forms of input that a user may enter, to the form that is provided to the IDNA functions. This functionality is now considered by the specification to be a local user-interface issue distinct from IDNA conversion functionality.

This library support one user-level mapping, that developed by the Unicode Consortium, known as Unicode IDNA Compatibility Processing. It provides for both regular mapping and transitional mapping.

For example, “Königsgäßchen” is not a permissible label as LATIN CAPITAL LETTER K is not allowed (as are capital letters in general). UTS46 will convert this into lower case.

>>> import idna
>>> idna.encode(u'Königsgäßchen')
idna.core.InvalidCodepoint: Codepoint U+004B at position 1 of u'K\xf6nigsg\xe4\xdfchen' not allowed
>>> idna.encode(u'Königsgäßchen', uts46=True)

Transitional processing provides conversions to help transition from the older 2003 standard to the current standard. For example, in the original IDNA specification, the LATIN SMALL LETTER SHARP S (ß) was converted into two LATIN SMALL LETTER S (ss), whereas in the current IDNA specification this conversion is not performed.

>>> idna.encode(u'Königsgäßchen', uts46=True, transitional=True)

Implementors should use transitional processing with caution, only in rare cases where conversion from legacy labels to current labels must be performed (i.e. IDNA implementations that pre-date 2008). For typical applications that just need to convert labels, transitional processing is unlikely to be beneficial and could produce unexpected incompatible results.

encodings.idna Compatibility

Function calls from the Python built-in encodings.idna module are mapping to their IDNA 2008 equivalents using the idna.compat module. Simply substitute the import clause in your code to refer to the new module name.


All errors raised during the conversion following the specification should raise an exception derived from the idna.IDNAError base class.

More specific exceptions that may be generated as idna.IDNABidiError when the error reflects an illegal combination of left-to-right and right-to-left characters in a label; idna.InvalidCodepoint when a specific codepoint is an illegal character in an IDN label (i.e. INVALID); and idna.InvalidCodepointContext when the codepoint is illegal based on its positional context (i.e. it is CONTEXTO or CONTEXTJ but the contextual requirements are not satisfied.)


The library has a test suite based on each rule of the IDNA specification, as well as test that are provided as part of the Unicode Technical Standard 46, Unicode IDNA Compatibility Processing.

The tests are run automatically on each commit to the master branch of the idna git repository at Travis CI:

File Type Py Version Uploaded on Size
idna-2.1-py2-none-any.whl (md5) Python Wheel 2.7 2016-03-20 52KB
idna-2.1-py2.py3-none-any.whl (md5) Python Wheel 2.7 2016-03-21 52KB
idna-2.1.tar.gz (md5) Source 2016-03-20 125KB