Sergey Biryukov

In jQuery 1.5+ (bundled with WordPress 3.2+), AJAX requests on sites with IDN domains don’t work in IE or Opera.
On Edit Post screen, adding a new category results in JS error:
<pre><code>Message: 'parsed.responses' - is null or not an object
</code></pre>
On Categories screen, adding a new category silently fails.
According to <a href="http://bugs.jquery.com/ticket/8419#comment:3" rel="nofollow ugc">jaubourg’s comment</a> in jQuery bug tracker, the request is considered cross-domain and, since IE doesn’t support cross-domain requests, AJAX won’t find a suitable transport and bail out.
This plugin implements a workaround suggested there by making AJAX requests relative.
WordPress Trac ticket: <a href="https://core.trac.wordpress.org/ticket/18952" rel="nofollow ugc">#18952</a>

IDN AJAX Workaround

Fixes AJAX requests on sites with IDN domains in IE and Opera.

dwright

This plugin adds IDN support to WordPress, making it an IDNA application. An IDN is a domain name that contains non-ascii characters. 
This plugin enables one to set the WordPress address (URL) to an IDN. (instead of the Punycode Representation)
Examples of an IDN:
<ul>
<li>bücher.ch</li>
<li>domæne.dk</li>
<li>nörgler.com</li>
<li>uddannelsesstøtte.dk</li>
<li>müller.de</li>
<li>räksmörgås.nu</li>
<li>画像.jp</li>
</ul>
<blockquote>
“An IDNA-enabled application is able to convert between the internationalised 
 and ASCII representations of a domain name. It uses the ASCII form for DNS 
 lookups but can present the internationalised form to users who presumably 
 prefer to read and write domain names in non-ASCII scripts such as Arabic or 
 Hiragana. Applications that do not support IDNA will not be able to handle 
 domain names with non-ASCII characters, but will still be able to access such 
 domains if given the (usually rather cryptic) ASCII equivalent.” – 
 <a href="http://en.wikipedia.org/wiki/Internationalized_domain_name" rel="nofollow ugc">IDN entry at Wikipedia</a>
</blockquote>
In simple terms, this plugin allows one to set their blog url to an IDN.
If you are interested in seeing what the PUNYCODE version of your IDN is, here is an <a href="http://mct.verisign-grs.com/conversiontool/" rel="nofollow ugc">online conversion tool</a>
As an example:
<blockquote>
Frau Müller has a blog and wants to use the IDN, http://www.müller.de 
 Currently, she would have to set the WP blog url, (General Settings menu) to 
 the Punycode version: xn--mller-kva.de, (which is the ascii representation 
 of müller.de) this would allow users using a IDN aware web browser to access 
 the site using the desired url: http://www.müller.de 
 (and also of course, xn--mller-kva.de).
It is more convenient for Frau Müller to use the actual IDN 
 http://www.müller.de as the WP blog url setting (General Settings menu), 
 this plugin enables that functionality.
</blockquote>
There are a few caveats with using this plugin, depending on what Browser, Operating 
System and versions used, one can get unexpected results.
Firefox >= 3.*
Firefox supports IDN’s but maintains a ‘whitelist’ of ‘safe’ domains. 
.com, .net, .eu are not white listed for safety reasons, so IDN’s on these 
domains will display as Punycode. <a href="https://support.mozilla.com/en-US/forum/1/545827" rel="nofollow ugc">see bug: </a>
There is an new (‘experimental’) Firefox add-on, 
<a href="https://addons.mozilla.org/en-US/firefox/addon/109224" rel="nofollow ugc">IDN Navbar</a>, which 
will enable all (whitelisted – Punycode) domains to display as IDN’s. 
So, if using Firefox and this plugin you (and your visitors) may want to install that addon.
Internet Explorer >= 7.*
Depending on your language set up, site’s that contain non ‘native language’ 
characters will display as Punycode and not the IDN. More info 
<a href="http://blogs.msdn.com/ie/archive/2006/07/31/684337.aspx" rel="nofollow ugc">msdn blogs</a> 
<a href="http://msdn.microsoft.com/en-us/library/bb250505(VS.85).aspx" rel="nofollow ugc">msdn libs1</a> 
<a href="http://msdn.microsoft.com/en-us/library/dd565654(VS.85).aspx" rel="nofollow ugc">msdn libs2</a>
Safari/Opera 10.* seem to display IDN’s for all domain’s fine. (untested)
<h3>Arbitrary section</h3>
WP plugins have a ‘stable tag’ requirement for distribution, however, at this 
time, I consider this plugin to be Beta quality at best.
It is possible to lock your self out of the administrative section of your blog
NOTE make sure you are using an IDN capable web browser when enabling this plugin. 
<a href="http://idn.icann.org/IDN-aware_software#Browsers" rel="nofollow ugc">More</a>
NOTE Unfortunely, Current Firefox versions display the Punycode version and 
NOT the IDN. For more details, (and work around) see the ‘Other Notes’ Link 
(Arbitrary section – readme.txt)
IE7/8, Safari, Opera10 all display the actual IDN, Firefox (and Chrome) 
navigation bar’s display the IDN as Punycode. (i.e. www.xn--)
There are some security issues with multi-byte chars and phishing, so this is 
Mozilla’s current approach, this may change in the future, as some folks are not 
happy about it.
https://bugzilla.mozilla.org/show_bug.cgi?id=542562 
another related, one: https://bugzilla.mozilla.org/show_bug.cgi?id=354592
Because this plugin effects how you access your site, installation is slightly more 
involved than most plugins.
If you installing this plugin, I would recommend, if possible, that it is the 
first thing you do on your blog, before you add any content, just in case 
something goes wrong, this will minimize downtime.
NOTE If something goes wrong and you cant access the WP admin area after 
changing your url, here are some instructions for 
<a href="https://codex.wordpress.org/Changing_The_Site_URL" rel="nofollow ugc">resetting your url</a>
Please report any bugs you find to the author of this plugin

IDNA

This plugin adds IDN support to Wordpress. IDN (Internationalized domain name) is a domain name that contains non-ascii characters.

IDN AJAX Workaround vs IDNA