What is CLS?

CLS is an abbreviation of Cumulative Layout Shift. But then you probably still don’t know anything. Perhaps you recognize the following situation. You go to a news site, start to read and during the reading the text moves. After some grumbling you continue to read on the new location of your last sentence. During the loading of the page, the text was already shown, but a banner had to be put somewhere in between afterwards.

This snafu became a ranking factor by Google. In other words, if your site contains many jumping texts, it will score worse in Google. CLS, together with FID and LCP, form the so called Core Web Vitals. And Core Web Vitals are part of Technical SEO.

If you want to know how a page on your website scores regarding CLS, there are several options. The easiest is to find an online version of the Google Lighthouse test. Here you can find an example. Another method is to install the Lighthouse plugin within a Chrome or Chromium browser.

Mind that Google and therefor the Lighthouse test, look at pages for desktop and mobile seperately. Depending on the test used, you might first need to select a device category. With others you can switch afterwards.

With the online version of the Lighthouse test, the homepage of my own website on desktop scores reasonably well regarding CLS score. In my defense I have to add that my new site just has gone live and optimisations are still underway. Lighthouse gives my homepage on desktop an orange rating with a CLS score of 0.102. If you run Lighthouse tests more often, you will notice that the color rating will get stricter over time. It might very well be that the same score will give red in half a year. Google becomes more strict over time as web watch dog.

If you want to enhance your CLS score and don’t know how, contact us.