Automatically enables subtitles on YouTube videos if available
// ==UserScript==
// @name YouTube Auto Turn on Subtitles
// @namespace http://tampermonkey.net/
// @version 0.1
// @description Automatically enables subtitles on YouTube videos if available
// @author Henry Suen
// @match https://www.youtube.com/watch*
// @grant none
// @run-at document-idle
// @license MIT
// ==/UserScript==
(function() {
'use strict';
// Main function to enable subtitles if available
function enableSubtitlesIfAvailable() {
console.log('YouTube Auto-Subtitles: Checking for subtitles...');
// Wait for video player to load
waitForElement('.html5-video-player').then((videoPlayer) => {
console.log('YouTube Auto-Subtitles: Video player found.');
// Check if subtitles are available but not enabled
checkSubtitlesStatus();
}).catch((error) => {
console.error('YouTube Auto-Subtitles: Error finding video player:', error);
});
}
// Function to wait for an element to appear in the DOM
function waitForElement(selector, timeout = 10000) {
return new Promise((resolve, reject) => {
const element = document.querySelector(selector);
if (element) {
return resolve(element);
}
const observer = new MutationObserver((mutations) => {
const element = document.querySelector(selector);
if (element) {
observer.disconnect();
resolve(element);
}
});
observer.observe(document.body, {
childList: true,
subtree: true
});
// Set timeout to avoid waiting forever
setTimeout(() => {
observer.disconnect();
reject(new Error(`Element ${selector} not found within ${timeout}ms`));
}, timeout);
});
}
// Check if subtitles are available and enable them if they're not already on
function checkSubtitlesStatus() {
// First, check if there's a subtitle button (indicating subtitles are available)
waitForElement('.ytp-subtitles-button').then((subtitleButton) => {
console.log('YouTube Auto-Subtitles: Subtitles button found.');
// Check if subtitles are already enabled (button is toggled on)
const isSubtitlesEnabled = subtitleButton.getAttribute('aria-pressed') === 'true';
if (!isSubtitlesEnabled) {
console.log('YouTube Auto-Subtitles: Enabling subtitles...');
subtitleButton.click();
console.log('YouTube Auto-Subtitles: Subtitles enabled.');
} else {
console.log('YouTube Auto-Subtitles: Subtitles are already enabled.');
}
}).catch((error) => {
console.log('YouTube Auto-Subtitles: Subtitles button not found, likely no subtitles available for this video.');
});
}
// Listen for page navigation events (YouTube is a SPA)
function setupNavigationListener() {
// Create an observer instance to detect URL changes
let lastUrl = location.href;
new MutationObserver(() => {
const currentUrl = location.href;
if (currentUrl !== lastUrl) {
lastUrl = currentUrl;
if (currentUrl.includes('youtube.com/watch')) {
console.log('YouTube Auto-Subtitles: URL changed, checking subtitles...');
setTimeout(enableSubtitlesIfAvailable, 1500); // Delay to ensure video player is loaded
}
}
}).observe(document, {subtree: true, childList: true});
}
// Initial execution
setTimeout(enableSubtitlesIfAvailable, 1500); // Initial delay to ensure video player is loaded
setupNavigationListener();
console.log('YouTube Auto-Subtitles: Script initialized.');
})();