Google
Cumulative Layout Shift
If you remember sometime in the past Google was telling us that your website needed to load really quickly to enhance your user’s speed experience. Essentially the faster the page loaded the better.
You may well have deferred your javascript and CSS? You may have moved all your javascript to the bottom of the page.
The net result was a fast loading page. This is now a problem and it’s a big problem.
When you load your website page do you see elements jump around as the page loads?
If you do, you will now fall victim to Google’s Cumulative Layout Shift, a new metric that will do you no good if your score is above 0.25.
Google is saying that CLS will impact your search positions in 2021, but we’re not sure exactly when in 2021.
Reference
- CLS (Cumulative Layout Shift): The amount that the page layout shifts during the loading phase. The score is rated from 0–1, where zero means no shifting and 1 means the most shifting. This is important because having page elements shift while a user is trying to interact with it is a bad user experience.
- Agg CLS (aggregated CLS) shown in the report is the lowest common CLS for 75% of visits to a URL in the group.
You can find recommendations on fixing these issues by running the PageSpeed Insights test on an affected URL.