It appears that Falkon doesn't support or let CORS policy to apply for GM API of GM.xmlHttpRequest Uncaught TypeError: GM.xmlHttpRequest is not a function If I coded the script right, then it is safe to say that it works with the original Greasemokney. Links: https://sourceforge.net/p/greasemonkey/wiki/GM_xmlhttpRequest/ http://greasemonkey.win-start.de/api/gm_xmlhttprequest.html https://wiki.greasespot.net/GM.xmlHttpRequest
*** This bug has been marked as a duplicate of bug 497082 ***