Cumulative Layout Shift: What It Is and How to Measure It - Deepstash

Bite-sized knowledge

to upgrade

your career

Ideas from books, articles & podcasts.

created 11 ideas


Cumulative Layout Shift: What It Is and How to Measure It

Cumulative Layout Shift: What It Is and How to Measure It


8 reads

Cumulative Layout Shift is one of these key metrics that measures the “jumpiness” of a website and how it unexpectedly moves as elements load. Let’s take a closer look at how this metric works, and how you can make sure your own website is following best practices so you rank higher on search eng...

Cumulative Layout Shift (or CLS) is a measure of how much a webpage unexpectedly shifts during its life. For example, if a website visitor loaded a page and, while they were reading it, banner loads and the page jumps down, that would constitute a large CLS score.

Along with Largest Content...

Page shifts happen when content loads at different speeds and causes the layout to change and alters what the viewer is looking at. Advertisements loading slowly, videos of unknown size suddenly appearing, or DOM elements being dynamically added are all potential causes of CLS.

Jumpy websites that load in pieces or with unexpected behavior will cause your visitors to find another website to browse. And if they do stick around, a high CLS score is likely to cause usability problems like choosing the wrong option, checking out too early, or missing parts of your website a...

The good news is that you don’t have to measure CLS yourself because Google makes it really easy to analyze your page performance with their PageSpeed Insights tool, or in the Chrome browser using Lighthouse Tools.

To analyze performance in PageSpeed Insights:

  • Enter a website URL...

  • Open up the website you want to analyze in Chrome.
  • Navigate to Developer Tools by clicking the three dots in the top right corner of the browser window, choosing “More Tools” and then “Developer Tools.”
  • When the console opens, choose “Lighthouse” from the options along the to...

These are the two variables that Google uses to calculate CLS in the formula below:

layout shift score = impact fraction x distance fraction

  • Impact fraction relates to the size of the unstable element in comparison to the viewport.

A good cumulative layout score is anything less than 0.1. The reports from PageInsights or Lighthouse tools will automatically flag any poor scores, as well as provide advice on how to optimize the page for better performance.

1. Use a CMS (content management system).

This will make sure that you’re designing with best practices in mind, and flag any issues before you launch your site.

2. Specify size attributes for images and videos.

Rather than letting them set their own height and width, dictate si...

CLS only takes into account unexpected changes. If the layout changes because of a user-initiated action, there is no impact on CLS. This is a helpful tool to use when you don’t need to load everything all at once. Instead, offer users the opportunity to choose which elements they want to view th...

Paying attention to CLS not only provides a better user experience, but it also boosts your search result rankings. It’s a win-win.

To meet Google’s standards for CLS, start by using a diagnostic tool to measure your website’s current performance. Take into account the basic guidelines outl...



It's time to




Jump-start your

reading habits

, gather your



remember what you read

and stay ahead of the crowd!

Takes just 5 minutes a day.


+2M Installs

4.7 App Score