flXHR is a flash+javascript solution for cross-domain Ajax communication. It implements an identical API to the native XHR object, which allows you to drop in flXHR into an existing page without any further code changes. This makes it particularly useful with Javascript frameworks like jQuery.

Since flXHR is emulating full compliant XHR, you will be able to make cross-domain calls for any kind of content, including HTML, text, binary, XML, JSON/P. You are not restricted to JSONP as you are with just core jQuery.

A common problem for every widget developer is getting data from the page to the server. The main obstacle is the cross-domain support or the lack there of. This is not as much as a problem when you're sending small amounts of the data - you can load scripts from other domains sending the data through the GET request. A completely different story is the sending of lots of data, where you would normally need a POST request. Until now there were just a few possible solutions - use a Flash cross-domain bridge and build your own browser extension being the most prominent.

Now on you can easily use a new technique, first presented by Kris Zyp who wrote a dojo implementation for it. I was hoping that somebody would port this to other libraries but since nobody did I decided to do it myself. And a week later you can download the jQuery plugin.

This plugin requires jQuery +1.3. that includes 1.3 beta releases (already out)

This tiny plugin provides a registry for different xhr implementations to co-exist.

If you want to provide a new implementation, you need to do this:

To use it, you do:

The built-in implementation is used by default (unless it's overriden with jQuery.ajaxSetup) and it's called 'xhr'.