Turn off/disable YouTube autoplay feature

disable_youtube_autoplay.js

// To run, install GreaseMonkey or TamperMonkey extension in your browser
// Copy this code into new user script, and enable
// !! If the toggle button is not been toggled automaticly:
// !! That means youtube changed for reasons the id of the toggle button again.
// !! In Chrome/Firefox: right-click the toggle button and choose "Inspect Element (Q)"
// !! You will find something like "<div id="TOGGLE_BUTTON_ID" class="toggle-button...."
// !! Copy whatever TOGGLE_BUTTON_ID is and replace down in "function disableAfterLoad()" the place holder named "TOGGLE_BUTTON_ID".
// !! Save script ctrl+S and reload youtube page.


// ==UserScript==
// @name         Disable Youtube autoplay
// @version      1.3
// @description  This script turns off Youtube's newest autoplay feature after the page loads
// @author       Jeff Bellucci, Jakob Wandel
// @match        *://www.youtube.com/*
// @run-at       document-end
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    let debug = false;

    let bottonIds = [];
    let i = 0;
    let MAX_TRIES = 5;
    bottonIds[i++] = 'toggle';
    bottonIds[i++] = 'toggleButton';
    bottonIds[i++] = 'improved-toggle';
    bottonIds[i++] = 'TOGGLE_BUTTON_ID';

    function debugMsg(msg){
     if(debug){
      console.log(msg);
     }
    }

    //https://stackoverflow.com/questions/2705583/how-to-simulate-a-click-with-javascript
    function eventFire(el, etype){
        if (el.fireEvent) {
            el.fireEvent('on' + etype);
        } else {
            var evObj = document.createEvent('Events');
            evObj.initEvent(etype, true, false);
            el.dispatchEvent(evObj);
        }
    }

    function disableAfterLoad(try_nr) {
        for (let key in bottonIds) {
            let autoplayToggle = document.getElementById(bottonIds[key]);
            if (autoplayToggle) {
                debugMsg("I found a Element called '"+bottonIds[key]+"'. I will now try to uncheck it:");
                if (autoplayToggle.hasAttribute('checked')) {
                    eventFire(autoplayToggle, 'click');
                    debugMsg("I assume, that if '"+bottonIds[key]+"' was the right Element, its now untoggled!");
                    delete bottonIds[key];
                    return;
                }else{
                    debugMsg("The element '"+bottonIds[key]+"' has no attribute checked. So I don't click it and check the other elements but not this one anymore.");
                    delete bottonIds[key];
                }
            } else {
                debugMsg("I could not finde an Element called '"+bottonIds[key]+"'. Maybe the site is not loaded jet? I will try again in 1 second.");
            }
        }
        if(try_nr > 0){
            try_nr--;
            setTimeout(function() {
               disableAfterLoad(try_nr);
            }, 1000);
        }
    }

    disableAfterLoad(MAX_TRIES);

})();

Thank you for your feedback! Yes Youtube changed things and now there is no click() function anymore at the toggle button to call.
So one has to attach it before calleing it. Thus Firefox had the same problem.

New version is v1.3. I tested it on Firefox and Chrome (newest public builds)

Also there is now a "debug mode" . Just set the variable debug to true and see the console.log

Oh sorry, I misunderstood. I thought this would stop clips from playing automatically when I load the page.
(This is the simplest, working one I found: https://greasyfork.org/en/scripts/36732-autoplay-disabled-for-youtube)

Ah, Yes sorry this scripts stops only YouTube from auto playing the next video. But your problem can be solved within the Browser Settings:
Firefox: https://support.mozilla.org/en-US/kb/block-autoplay (thats per default activated)
Chrome: "Launch Chrome and in the Address Bar type: chrome://flags/#autoplay-policy and hit Enter. That will bring you directly to the flag that you need to change. From the drop-down box, change the setting from Default to “Document user activation is required” and relaunch the browser." (source: https://www.groovypost.com/howto/disable-autoplay-videos-on-sites-in-google-chrome/)

Thanks. But this only works when the tab is in the background. As soon as I put it in foreground it plays.
Well, the userscript works. All is good. :)