Redirect facebook.com/messenger to messenger.com
// ==UserScript==
// @name Messenger Redirect
// @namespace http://tampermonkey.net/
// @version 1.0
// @description Redirect facebook.com/messenger to messenger.com
// @author Darkha
// @match *://*.facebook.com/messages/t/*
// @grant none
// @run-at document-start
// ==/UserScript==
(function() {
'use strict';
window.location.replace("https://www.messenger.com/t/" + /facebook.com\/messages\/t\/(.*?)\?/.exec(window.location.href + '?')[1]);
// Your code here...
})();