Tampermonkey script preventing autoplay in YouTube on Chrome

YouTube — disable autoplay until I press Play-2.0.0.user.js

// ==UserScript==
// @name         YouTube — disable autoplay until I press Play
// @namespace    local.dmitry.youtube.autoplay.block
// @version      2.0.0
// @description  Prevent YouTube videos from auto-playing on open; only play after a recent user gesture.
// @author       you
// @match        https://www.youtube.com/*
// @run-at       document-start
// @grant        none
// ==/UserScript==

(function () {
  'use strict';

  // Allow play only if there was a user gesture in the last N ms
  const GESTURE_WINDOW_MS = 600;

  let lastGestureTs = 0;

  // Count clicks/taps/keyboard as gestures
  const markGesture = () => { lastGestureTs = Date.now(); };
  window.addEventListener('pointerdown', markGesture, true);
  window.addEventListener('keydown', markGesture, true);

  // Helper: pause if the play wasn't user-initiated
  function guardPlay(ev) {
    const v = ev.target;
    if (!(v instanceof HTMLVideoElement)) return;

    const recentGesture = (Date.now() - lastGestureTs) <= GESTURE_WINDOW_MS;

    // If no recent gesture, immediately pause (blocks autoplay)
    if (!recentGesture) {
      // Prevent “play” from continuing
      try { v.pause(); } catch {}
      // Mark as not playing
      v.__blockedOnce = true;
    }
  }

  // On first attachment and on SPA navigations, ensure listeners exist and pause if already playing
  function attachToAllVideos() {
    document.querySelectorAll('video').forEach(v => {
      if (v.__autoplayGuardAttached) return;
      v.__autoplayGuardAttached = true;

      // If YouTube already started it, stop it right away
      try {
        if (!v.paused) v.pause();
      } catch {}

      // Listen in capture so we run before player handlers
      v.addEventListener('play', guardPlay, true);
    });
  }

  // Observe DOM for new video elements (YouTube swaps them frequently)
  const mo = new MutationObserver(() => attachToAllVideos());
  mo.observe(document.documentElement, { childList: true, subtree: true });

  // Handle YouTube SPA events (navigations without full reload)
  window.addEventListener('yt-navigate-finish', () => {
    // Reset gesture; a new page shouldn’t auto-play
    lastGestureTs = 0;
    attachToAllVideos();
    // If a video element already exists, pause it once more
    const v = document.querySelector('video');
    if (v) { try { v.pause(); } catch {} }
  });

  // First pass (for hard reloads or when run-at is late)
  attachToAllVideos();
})();