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Balanced YouTube loading optimizations with lazy loading, smart preloading, hover previews, and scrubbing control.
// ==UserScript==
// @name easystrapper (for youtube)
// @namespace http://tampermonkey.net/
// @version 2025-01-18
// @description Balanced YouTube loading optimizations with lazy loading, smart preloading, hover previews, and scrubbing control.
// @license MIT
// @author ondry4k
// @match https://www.youtube.com/
// @icon https://www.google.com/s2/favicons?sz=64&domain=youtube.com
// @grant none
// ==/UserScript==
(function () {
'use strict';
const CONFIG = {
preloadMargin: '500px 0px',
loadMargin: '200px 0px',
hoverDelayMs: 160,
maxPreloads: 80,
maxCachedPreloads: 160,
maxScriptPreloads: 4,
debug: true,
debugVerbose: true,
refreshMs: 2500,
cacheCompareMs: 12000,
maxCompareSamples: 6,
disableMiniPlayer: true,
disableRelatedSidebar: true,
disableSkeletons: true,
disableShimmer: true,
disablePrefetchRelated: true
};
const THUMB_SELECTOR = 'ytd-thumbnail img, a#thumbnail img, img#img';
const VID_REGEX = /\/vi\/([\w-]{6,})\//;
const processed = new WeakSet();
const hoverTimers = new WeakMap();
const preloaded = new Set();
const previewCache = new Map();
const thumbCache = new Map();
const hintHosts = new Set();
const scriptStart = performance.now();
let preloadObserver;
let loadObserver;
let scrubObserver;
let persistTimer;
let mutationTimer;
let refreshTimer;
let scrollTicking = false;
let compareTimer;
let mutationObserver;
let hoverAttached = false;
let scrollAttached = false;
let cssInjected = false;
function log(label, message, data) {
if (!CONFIG.debug) return;
const styles = {
init: 'color:#0ea5e9;font-weight:600',
preload: 'color:#22c55e;font-weight:600',
load: 'color:#eab308;font-weight:600',
scrub: 'color:#f97316;font-weight:600',
hover: 'color:#8b5cf6;font-weight:600',
script: 'color:#14b8a6;font-weight:600',
cache: 'color:#10b981;font-weight:600',
perf: 'color:#38bdf8;font-weight:600',
net: 'color:#f43f5e;font-weight:600'
};
const style = styles[label] || 'color:#94a3b8';
if (typeof data !== 'undefined') {
console.log(`%c[easystrapper] ${message}`, style, data);
return;
}
console.log(`%c[easystrapper] ${message}`, style);
}
function safeRun(label, fn) {
try {
fn();
} catch (err) {
log('net', `Safeguard: ${label} failed`, err);
}
}
function loadPersistedPreloads() {
try {
const raw = sessionStorage.getItem('easystrapper_preloads');
if (!raw) return;
const items = JSON.parse(raw);
if (Array.isArray(items)) {
items.forEach((url) => preloaded.add(url));
if (CONFIG.debugVerbose) {
log('cache', `Preload cache restored (${items.length})`);
}
}
} catch (err) {
// ignore storage issues
}
}
function comparePreloadCache() {
if (!CONFIG.debug || !CONFIG.debugVerbose) return;
let stored = [];
try {
const raw = sessionStorage.getItem('easystrapper_preloads');
stored = raw ? JSON.parse(raw) : [];
} catch (err) {
stored = [];
}
const storedSet = new Set(Array.isArray(stored) ? stored : []);
const inMemoryOnly = [];
preloaded.forEach((url) => {
if (!storedSet.has(url)) inMemoryOnly.push(url);
});
const inStorageOnly = [];
storedSet.forEach((url) => {
if (!preloaded.has(url)) inStorageOnly.push(url);
});
log(
'cache',
`Cache compare mem:${preloaded.size} storage:${storedSet.size} memOnly:${inMemoryOnly.length} storageOnly:${inStorageOnly.length}`
);
const sample = inMemoryOnly.slice(0, CONFIG.maxCompareSamples);
if (sample.length) {
log('cache', 'Mem-only sample', sample);
}
}
function injectCss() {
if (cssInjected) return;
const rules = [];
if (CONFIG.disableMiniPlayer) {
rules.push(
'ytd-miniplayer, ytd-miniplayer-bar-renderer, #miniplayer, ytd-player-minimized { display: none !important; }'
);
}
if (CONFIG.disableRelatedSidebar) {
rules.push('#related, ytd-watch-next-secondary-results-renderer { display: none !important; }');
}
if (CONFIG.disableSkeletons) {
rules.push('ytd-skeleton, .ytd-skeleton, yt-page-skeleton { display: none !important; }');
}
if (CONFIG.disableShimmer) {
rules.push('.shimmer, .ytp-swatch-background-color, .ytp-shimmer { animation: none !important; }');
}
if (!rules.length) return;
const style = document.createElement('style');
style.id = 'easystrapper-style';
style.textContent = rules.join('\n');
document.head.appendChild(style);
cssInjected = true;
log('init', 'UI trims applied');
}
function persistPreloads() {
if (persistTimer) return;
persistTimer = window.setTimeout(() => {
persistTimer = null;
const items = Array.from(preloaded).slice(-CONFIG.maxCachedPreloads);
try {
sessionStorage.setItem('easystrapper_preloads', JSON.stringify(items));
if (CONFIG.debugVerbose) {
log('cache', `Preload cache saved (${items.length})`);
}
} catch (err) {
// ignore storage issues
}
}, 300);
}
function isThumbnail(img) {
return img.matches(THUMB_SELECTOR);
}
function getVideoIdFromUrl(url) {
if (!url) return null;
try {
const parsed = new URL(url, location.origin);
const id = parsed.searchParams.get('v');
if (id) return id;
} catch (err) {
// ignore
}
const match = url.match(VID_REGEX);
return match ? match[1] : null;
}
function getVideoId(el) {
if (!el) return null;
if (el.dataset && el.dataset.esVid) return el.dataset.esVid;
const link = el.closest('a#thumbnail, a[href*="watch"]');
if (link && link.href) {
const fromLink = getVideoIdFromUrl(link.href);
if (fromLink) {
if (el.dataset) el.dataset.esVid = fromLink;
if (CONFIG.debugVerbose) {
log('cache', 'Video id cached', fromLink);
}
return fromLink;
}
}
const fromImg = getVideoIdFromUrl(el.currentSrc || el.src);
if (fromImg && el.dataset) {
el.dataset.esVid = fromImg;
if (CONFIG.debugVerbose) {
log('cache', 'Video id cached', fromImg);
}
}
return fromImg;
}
function getThumbUrl(videoId, quality) {
if (!videoId) return null;
const key = `${videoId}:${quality}`;
if (thumbCache.has(key)) return thumbCache.get(key);
const url = `https://i.ytimg.com/vi/${videoId}/${quality}.jpg`;
thumbCache.set(key, url);
return url;
}
function getPreviewUrl(videoId) {
if (!videoId) return null;
if (previewCache.has(videoId)) return previewCache.get(videoId);
const url = `https://i.ytimg.com/an_webp/${videoId}/mqdefault_6s.webp`;
previewCache.set(videoId, url);
return url;
}
function makePreload(url, asType) {
if (!url || preloaded.has(url) || preloaded.size >= CONFIG.maxPreloads) {
if (CONFIG.debugVerbose && url && preloaded.has(url)) {
log('cache', `Preload cache hit (${asType || 'image'})`, url);
}
return;
}
const link = document.createElement('link');
link.rel = 'preload';
link.as = asType || 'image';
link.href = url;
document.head.appendChild(link);
preloaded.add(url);
persistPreloads();
log('preload', `Preload queued (${asType || 'image'})`, url);
}
function tuneImage(img) {
if (processed.has(img)) return;
processed.add(img);
if (!img.loading) img.loading = 'lazy';
img.decoding = 'async';
img.fetchPriority = 'low';
}
function softenScrub(img, videoId) {
if (!img || !videoId || !img.src) return;
if (img.src.includes('an_webp') || img.src.includes('/sb/')) {
const staticUrl = getThumbUrl(videoId, 'hqdefault');
if (staticUrl && staticUrl !== img.src) {
img.src = staticUrl;
log('scrub', 'Scrub thumbnail softened', staticUrl);
}
}
}
function teardownObservers() {
if (preloadObserver) preloadObserver.disconnect();
if (loadObserver) loadObserver.disconnect();
if (scrubObserver) scrubObserver.disconnect();
preloadObserver = null;
loadObserver = null;
scrubObserver = null;
}
function setupObservers() {
teardownObservers();
preloadObserver = new IntersectionObserver((entries) => {
entries.forEach((entry) => {
if (!entry.isIntersecting) return;
const img = entry.target;
const videoId = getVideoId(img);
const preloadUrl = getThumbUrl(videoId, 'hqdefault') || img.currentSrc || img.src;
makePreload(preloadUrl, 'image');
if (CONFIG.debugVerbose) {
log('preload', 'Near viewport detected', preloadUrl);
}
});
}, { rootMargin: CONFIG.preloadMargin, threshold: 0.01 });
loadObserver = new IntersectionObserver((entries) => {
entries.forEach((entry) => {
if (!entry.isIntersecting) return;
const img = entry.target;
const videoId = getVideoId(img);
const highRes = getThumbUrl(videoId, 'hqdefault');
if (highRes && img.src !== highRes) {
img.src = highRes;
log('load', 'Thumbnail upgraded', highRes);
}
img.fetchPriority = 'auto';
});
}, { rootMargin: CONFIG.loadMargin, threshold: 0.01 });
scrubObserver = new IntersectionObserver((entries) => {
entries.forEach((entry) => {
if (entry.isIntersecting) return;
const img = entry.target;
const videoId = getVideoId(img);
softenScrub(img, videoId);
});
}, { rootMargin: '0px', threshold: 0.01 });
}
function observeThumbnail(img) {
if (!preloadObserver || !loadObserver || !scrubObserver) return;
preloadObserver.observe(img);
loadObserver.observe(img);
scrubObserver.observe(img);
}
function getImagesFromRoot(root) {
const scope = root || document;
const images = [];
if (scope.nodeType === 1 && scope.tagName === 'IMG') {
images.push(scope);
}
scope.querySelectorAll('img').forEach((img) => images.push(img));
return images;
}
function applyOptimizations(root) {
const images = getImagesFromRoot(root);
images.forEach((img) => {
tuneImage(img);
if (isThumbnail(img)) {
observeThumbnail(img);
}
});
}
function preloadScripts() {
const scripts = Array.from(document.querySelectorAll('script[src]'));
scripts.slice(0, CONFIG.maxScriptPreloads).forEach((script) => {
makePreload(script.src, 'script');
});
if (scripts.length) {
log('script', 'Script preloads scheduled', scripts.length);
}
}
function preloadStaticImages(root) {
const scope = root || document;
const staticImages = scope.querySelectorAll(
'ytd-guide-entry-renderer img, ytd-mini-guide-entry-renderer img, ytd-channel-avatar img, ' +
'#avatar img, yt-img-shadow img, ytd-topbar-logo-renderer img, ytd-searchbox img, ' +
'ytd-video-owner-renderer #channel-info img'
);
staticImages.forEach((img) => {
if (!img || img.dataset.esStaticPreloaded) return;
const url = img.currentSrc || img.src;
if (!url) return;
img.dataset.esStaticPreloaded = '1';
makePreload(url, 'image');
img.fetchPriority = 'low';
if (CONFIG.debugVerbose) {
log('preload', 'Static image cached', url);
}
});
}
function setupNetworkHints() {
const hosts = [
'https://www.youtube.com',
'https://i.ytimg.com',
'https://i9.ytimg.com'
];
hosts.forEach((host) => {
if (hintHosts.has(host)) return;
['preconnect', 'dns-prefetch'].forEach((rel) => {
const link = document.createElement('link');
link.rel = rel;
link.href = host;
link.crossOrigin = 'anonymous';
document.head.appendChild(link);
});
hintHosts.add(host);
});
log('net', 'Network hints applied', Array.from(hintHosts));
}
function disableUnrelatedPrefetch() {
if (!CONFIG.disablePrefetchRelated) return;
const currentId = getVideoIdFromUrl(location.href);
const links = Array.from(document.querySelectorAll(
'link[rel="prefetch"], link[rel="prerender"], link[rel="preload"][as="fetch"]'
));
let removed = 0;
links.forEach((link) => {
const href = link.href || '';
if (!href || !href.includes('watch?v=')) return;
const targetId = getVideoIdFromUrl(href);
if (!currentId || targetId !== currentId) {
link.remove();
removed += 1;
}
});
if (removed && CONFIG.debugVerbose) {
log('net', `Prefetch hints trimmed (${removed})`);
}
}
function scheduleIdleWork() {
const idle = window.requestIdleCallback || function (cb) { return setTimeout(cb, 200); };
idle(preloadScripts, { timeout: 800 });
}
function attachHoverPreview() {
if (hoverAttached) return;
document.addEventListener('pointerenter', (event) => {
const target = event.target;
if (!(target instanceof Element)) return;
const container = target.closest('a#thumbnail, ytd-thumbnail');
if (!container) return;
const img = container.querySelector('img');
if (!img) return;
const videoId = getVideoId(img);
if (!videoId) return;
if (hoverTimers.has(img)) {
clearTimeout(hoverTimers.get(img));
}
const timer = window.setTimeout(() => {
img.dataset.esOriginalSrc = img.src;
const previewUrl = getPreviewUrl(videoId);
if (previewUrl) {
img.src = previewUrl;
makePreload(previewUrl, 'image');
log('hover', 'Hover preview active', previewUrl);
}
}, CONFIG.hoverDelayMs);
hoverTimers.set(img, timer);
}, true);
document.addEventListener('pointerleave', (event) => {
const target = event.target;
if (!(target instanceof Element)) return;
const container = target.closest('a#thumbnail, ytd-thumbnail');
if (!container) return;
const img = container.querySelector('img');
if (!img) return;
if (hoverTimers.has(img)) {
clearTimeout(hoverTimers.get(img));
hoverTimers.delete(img);
}
if (img.dataset.esOriginalSrc) {
img.src = img.dataset.esOriginalSrc;
delete img.dataset.esOriginalSrc;
log('hover', 'Hover preview cleared');
}
}, true);
hoverAttached = true;
}
function shouldProcessNode(node) {
if (node.nodeType !== 1) return false;
const el = node;
if (el.tagName === 'IMG') return true;
if (el.matches('ytd-thumbnail, ytd-rich-item-renderer, ytd-video-renderer, ytd-grid-video-renderer, ytd-compact-video-renderer')) {
return true;
}
if (el.querySelector && el.querySelector('img, ytd-thumbnail, ytd-rich-item-renderer, ytd-video-renderer, ytd-grid-video-renderer, ytd-compact-video-renderer')) {
return true;
}
return false;
}
function observeDOM() {
if (mutationObserver) return;
mutationObserver = new MutationObserver((mutations) => {
if (mutationTimer) return;
mutationTimer = window.setTimeout(() => {
mutationTimer = null;
mutations.forEach((mutation) => {
mutation.addedNodes.forEach((node) => {
if (!shouldProcessNode(node)) return;
applyOptimizations(node);
preloadStaticImages(node);
});
});
}, 120);
});
mutationObserver.observe(document.body, { childList: true, subtree: true });
}
function runContinuousOptimization(reason) {
const idle = window.requestIdleCallback || function (cb) { return setTimeout(cb, 120); };
idle(() => {
const start = performance.now();
applyOptimizations(document);
preloadStaticImages(document);
scheduleIdleWork();
if (reason === 'interval') {
disableUnrelatedPrefetch();
}
if (reason) {
const elapsed = Math.round(performance.now() - start);
log('perf', `Continuous optimize (${reason}) in ${elapsed}ms`);
}
}, { timeout: 800 });
}
function startContinuousOptimization() {
if (refreshTimer) return;
refreshTimer = window.setInterval(() => {
runContinuousOptimization('interval');
}, CONFIG.refreshMs);
compareTimer = window.setInterval(comparePreloadCache, CONFIG.cacheCompareMs);
if (scrollAttached) return;
window.addEventListener('scroll', () => {
if (scrollTicking) return;
scrollTicking = true;
window.requestAnimationFrame(() => {
scrollTicking = false;
runContinuousOptimization('scroll');
});
}, { passive: true });
scrollAttached = true;
}
function init() {
const initStart = performance.now();
safeRun('setup observers', setupObservers);
safeRun('network hints', setupNetworkHints);
safeRun('ui trims', injectCss);
safeRun('apply optimizations', () => applyOptimizations(document));
safeRun('preload static images', () => preloadStaticImages(document));
safeRun('hover preview', attachHoverPreview);
safeRun('dom observer', observeDOM);
safeRun('idle work', scheduleIdleWork);
safeRun('continuous optimize', startContinuousOptimization);
safeRun('prefetch trims', disableUnrelatedPrefetch);
const initElapsed = Math.round(performance.now() - initStart);
const totalElapsed = Math.round(performance.now() - scriptStart);
log('init', `Easystrapper initialized in ${initElapsed}ms (since script start ${totalElapsed}ms)`);
}
loadPersistedPreloads();
window.addEventListener('load', init);
document.addEventListener('yt-navigate-finish', init);
})();