To restore animated thumbnail previews, requires inline video previews to be disabled in your YouTube user settings. Note: not Greasemonkey compatible. v3 Add fix for new youtube update to sidebar vids; remove carousel fallback.
// ==UserScript==
// @name Restore animated thumbnail previews - youtube.com
// @namespace Violentmonkey Scripts seekhare
// @match http*://www.youtube.com/*
// @run-at document-start
// @version 3.0
// @license MIT
// @author seekhare
// @description To restore animated thumbnail previews, requires inline video previews to be disabled in your YouTube user settings. Note: not Greasemonkey compatible. v3 Add fix for new youtube update to sidebar vids; remove carousel fallback.
// ==/UserScript==
const logHeader = 'UserScript Restore YT Animated Thumbs:';
console.log(logHeader, "enabled.")
Object.defineProperties(Object.prototype,{isPreviewDisabled:{get:function(){return false}, set:function(){}}}); // original method
//2025-07-12 added animatedThumbnailEnabled & inlinePreviewEnabled
Object.defineProperties(Object.prototype,{animatedThumbnailEnabled:{get:function(){return true}, set:function(){}}});
Object.defineProperties(Object.prototype,{inlinePreviewEnabled:{get:function(){return false}, set:function(){}}});
//2025-07-12 Don't enable the below as seems to break things but I'm leaving here in case of future Youtube change, for reference if needed in future fixes.
//Object.defineProperties(Object.prototype,{isInlinePreviewEnabled:{get:function(){return false}, set:function(){}}});
//Object.defineProperties(Object.prototype,{isInlinePreviewDisabled:{get:function(){return true}, set:function(){}}});