When developers think about performance optimization, they usually focus on things like:

lazy loading

caching

image optimization

bundle size

And while those things absolutely matter there’s another area that heavily impacts user experience -> Loading states and layout stability.

A badly implemented loading experience can make an app feel slow, jumpy, or frustrating to use. This is strongly connected to an important Core Web Vital metric Cumulative Layout Shift (CLS).

In this article, we’ll explore:

What CLS is

Why loaders are critical for perceived performance

How poor loading states hurt UX

Practical examples in Vue

Best practices for stable layouts

Let’s dive in.

🤔 What Is Cumulative Layout Shift (CLS)?

CLS measures how much elements unexpectedly move during page loading.

Example of bad CLS:

Text suddenly jumps down

Buttons move while you try to click

Images appear late and push content around

We’ve all experienced websites like this:

👉 You try to click something… and suddenly the…