This allows All browser users to download and convert YouTube videos to mp3 (320) kbps files and also videos with a variety of high quality options 2160p (4k), 1440p (2k), 1080p (HD), 720p (HD), 480p, 360p, 144p etc. This video quality is supported for all available video formats (MP4, WEBM, 3GP). Then Visit https://www.youtube.com/new

YoutubeDownloader.user.js

// ==UserScript==
// @name            Vevioz Youtube Downloader
// @description     This extension add a download tab button on any Youtube page and allows you to download MP3 & Video with just one click (1080,2K,4K,8K Ultra High Definition Supported).
// @icon            https://assets.vevioz.com/addons/images/favicon.ico
//
// @author          Vevioz Enterprise
// @namespace       https://developers.vevioz.com
//
// @license         GPLv3 - https://www.gnu.org/licenses/gpl-3.0.txt
// @copyright       Copyright (C) 2022, by Developer.vevioz.com
// @include         https://www.youtube.com/*
// @include         https://www.youtube.com/*
//
// @version         7.6
//
// @run-at          document-end
// @unwrap
// ==/UserScript==

dwld_btn_onclick = function (){
  var path ='https://addons.vevioz.com/?id='+encodeURIComponent(getYT(window.location));
  window.open(path,'_blank');
};

getYT = function(url){
    var regExp = /^.*((youtu.be\/)|(v\/)|(\/u\/\w\/)|(embed\/)|(watch\?))\??v?=?([^#\&\?]*).*/;
    var match = String(url).match(regExp);
    return (match&&match[7].length==11)? match[7] : false;
};
getSpan = function(text, className) {
    var _tn = document.createTextNode(text);
    var span = document.createElement("span");
    span.className = className;
    span.appendChild(_tn);
    return span;
};
var myAppInterface = {
  init:function(){
    this.insertGlobalCSS();
  },
  addGlobalStyle: function(doc, css) {
    if(document.querySelector('.easy-youtube-mp3-css'))return;
    var head = doc.getElementsByTagName('head')[0];
    if (!head) {return; }
    var style = doc.createElement('style');
    style.id = 'easy-youtube-mp3-css';
    style.type = 'text/css';
    if (style.styleSheet) {
      style.styleSheet.cssText = css;
    } else {
      style.appendChild(document.createTextNode(css));
    }
    head.appendChild(style);
  },
  insertGlobalCSS: function(){
    var css = function (){
      /*start
      #downloadyoutubemp3.ytd-watch{padding-top:0px;overflow: auto;padding-bottom: 10px;margin-right:10px}
      #downloadyoutubemp3 .dwld_btn{background-color: #f16310;border: #f16310;border-radius: 2px;color: #FFF;padding: 10px 16px; font-size: 1.4em;cursor:pointer;display:inline-block}
      #downloadyoutubemp3 .dwld_btn:hover{background-color: #f16310}
      @media (min-width: 657px){ytd-watch[theater] #downloadyoutubemp3.ytd-watch{margin-right:24px}}
      end*/
    }.toString().replace("/*start",'').replace("end*/",'').slice(14,-1);
    this.addGlobalStyle(document, css);
  },
};

createButton = function() {
    var obj = document.querySelector('#top-level-buttons-computed');
    if(obj !== null){
        // check if the button has already been created
        var btnRow = document.getElementById('downloadyoutubemp3');
        if(btnRow === null){
            myAppInterface.init();
            var downloadyoutubemp3 = document.createElement("div");
            downloadyoutubemp3.id = "downloadyoutubemp3";
            downloadyoutubemp3.className = "style-scope ytd-watch";

            var dwld_btn = document.createElement("div");
            dwld_btn.className = "style-scope dwld_btn";

            dwld_btn.appendChild(getSpan("DOWNLOAD"));

            dwld_btn.onclick = dwld_btn_onclick;

            obj.parentNode.insertBefore(downloadyoutubemp3, obj);
            downloadyoutubemp3.appendChild(dwld_btn);
        }
    }
};

// yt does make use of some bogus AJAX functionality which breaks pagemod
// we have to check in intervals if the document has been replaced by yt to
// recreate the button if needed.
var intervalCheck = setInterval(function(){ createButton();}, 250);