Core Web Vitals: Understanding CLS

What is CLS and why does it matter?

Cumulative Layout Shift (CLS) is a metric that measures the visual stability of a web page. It quantifies how much elements on a page move around unexpectedly as the page loads and interacts with the user. A high CLS score indicates a poor user experience, as sudden shifts can disrupt tasks and lead to frustration.

How is CLS measured?

CLS is measured in units of fractional pixels. A value of 0.1 means that elements on the page moved by an average of 1/10th of a pixel during the page load. A value of 0.25 means that elements moved by an average of 1/4th of a pixel.

What is considered good, needs improvement, or poor?

Good: A CLS score of 0.1 or lower is considered good.
Needs improvement: A CLS score between 0.1 and 0.25 is considered to need improvement.
Poor: A CLS score of 0.25 or higher is considered poor.

Why is CLS important?

A low CLS score is essential for providing a positive user experience. When elements on a page shift unexpectedly, it can disrupt tasks, lead to frustration, and even cause accidental clicks. A high CLS score can also negatively impact your website’s search engine ranking.

How can you improve CLS?

There are several ways to improve CLS, including:

Loading images and other resources efficiently.
Avoiding dynamic content that changes the layout of the page.
Using a responsive design that adapts to different screen sizes.
Using CSS Grid or Flexbox for layout.

By understanding CLS and taking steps to improve it, you can create a better user experience for your website visitors.

Sources: Digital Economy Discussions, Undercode Ai & Community, Internet Archive, Wikipedia, Chromiumdev
Image Source: OpenAI, Undercode AI DI v2