Question

Has anybody had any luck performing cross origin XHRs from a user script in Google Chrome? The requests go through to the server (I can see them in the logs) but, the readystatechanged event is never fired.

Extension permissions don’t seem to be doing the trick. Neither is JSONP.

Answer 1

Current versions of Chrome (13.0.781 or later) now support most or all of the GM_xmlhttpRequest()^Doc functionality — including cross-domain requests.
See Issue 18857: Support cross-site XMLHttpRequest in content scripts.

So this script works perfectly fine now on Chrome (and Firefox, of course):

// ==UserScript==
// @name            _Cross domain (XSS) GM_xmlhttpRequest, Chrome too
// @include         http://stackoverflow.com/*
// @grant           GM_xmlhttpRequest
// ==/UserScript==

GM_xmlhttpRequest ( {
    method:     "GET",
    url:        "http://www.google.com/",
    onload:     function (response) {
                    console.log (   response.status,
                                    response.responseText.substring (0, 80)
                                );
                }
} );

(Install that script, then browse any SO page. The script will write the first 80 characters of the Google home page to the console.)