Does not use passive listeners to improve scrolling performance

Overview

Browsers like Chrome normally block page scrolling during the initial page load until JavaScript has executed. With JavaScript already blocking the main-thread, smooth scrolling is not possible, this in turn reduces visitors’ page experience.

Passive event listeners resolve this issue, allowing you to improve your visitors’ experience.

How to fix this?

Add a passive: true flag to every event listener flagged by GTmetrix. For example,

document.addEventListener('touchstart', onTouchStart, {passive: true});