This is really annoying if you load a page

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If your CSS – which controls all the styling of your page – is deferred, then the contents of the page can load before the CSS rules are applied. This means that the contents of your page will load unstyled, and then jump about a bit as the CSS loads in.  and click on a link, but then the link jumps and you click on the wrong link. If you’re a bit OCD like me, such experiences are absolutely infuriating (even though they only cost seconds of time). Due to site owners attempting to “game” page speed ratings by deferring all resources, Google needed a counter-metric, which would offset all the page speed gains against the user experience deficit. Enter Cumulative Layout Shift (CLS).

This is one tricky customer, who is out to ruin your DB to Data if you try to broad-brush apply page speed boosts without thinking of your users. CLS will basically analyze your page loads for glitchy shifts and delayed CSS rules. If there are too many, you will fail the Core Web Vitals assessment despite having satisfied all speed-related metrics. Assessing your Core Web Vitals for better UX and SEO results One of the best ways to analyze a single webpage’s performance is to load it into PageSpeed Insights. The view is split into a combination of: URL-level data. Origin (domain-level) data. Lab data.



Field data. To make sense of this, we need to look at an example Here, we can see the page speed ratings and metrics for the TechCrunch homepage. Image 92 Above, you can see that the Core Web Vitals Assessment has failed. In a mobile-first web, it’s important to select the Mobile results tab, which should be rendered by default (these are the results that really matter). Select the Origin toggle so you see general data averaged across your site’s domain rather than just the homepage (or whichever page you put in to scan).