Automatically enable the subtitles.
// ==UserScript==
// @name Youtube - Subtitle
// @namespace https://greasyfork.org/en/users/670188-hacker09?sort=daily_installs
// @version 3
// @description Automatically enable the subtitles.
// @author hacker09
// @match https://*.youtube.com/embed/*
// @match https://www.youtube.com/watch?v=*
// @icon https://www.youtube.com/s/desktop/03f86491/img/favicon.ico
// @run-at document-end
// @grant none
// ==/UserScript==
(function() {
'use strict';
document.querySelector('video').addEventListener('playing', () => { //When the video is played
document.querySelector(".ytp-subtitles-button.ytp-button").innerHTML.match('unavailable') === null && document.querySelector(".ytp-subtitles-button.ytp-button").ariaPressed === 'false' ? document.querySelector(".ytp-subtitles-button.ytp-button").click() : ''; //Auto enable the subtitles if available and they are disabled
}, { once: true }); //Finishes the timeupdate event listener
})();