CODEWITHSUNDEEP
google-search-consolecore-web-vitals
David Yunevich
David Yunevich

Reputation: 194

Core Web Vitals CLS fails, but Page Speed Insights and Lighthose shows CLS = 0

Our website https://blog.servermania.com fails CLS for Core Web Vitals report.

We've fixed it, and currently, Page Speed Insights shows CLS = 0. However, after running validation in Google Search Console, we still got the same CLS issue in Core Web Vitals.

My only guess is that we didn't clear Cloudflare cache before starting the validation, but maybe it's something else? Does anybody have the same problem?

Upvotes: 2

Views: 1608

Answers (1)

Rick Viscomi
Rick Viscomi

Reputation: 8852

PageSpeed Insights shows CLS from two environments: real users and lab/synthetic tests. I can confirm that PSI reports your lab CLS is 0.0 for both desktop and mobile:

enter image description here

However, the real-user CLS does show some issues. One major complication is that there's not enough data for your home page to see any real-user stats, so PSI is falling back to data across all pages on your website (AKA origin). Let's look at the origin-level CLS anyway.

On desktop it's rated "good" but slightly higher than 0.0:

enter image description here

0.1 is the threshold after which it's no longer good, so at 0.08 you're getting close to failing the Core Web Vitals assessment.

On mobile things are much different:

enter image description here

Your mobile users experience a CLS score of 0.32 (at the 75th percentile) which blows past the "good" threshold of 0.1, and into "poor" territory.

The fact that Lighthouse isn't corroborating this with the lab CLS suggests that one of two (or both) things are at play: there are user-dependent factors contributing to poor CLS, or we're not auditing the page with actual CLS issues. For example, if CLS is induced by scrolling or clicking, Lighthouse won't necessarily capture those layout shifts. Also, it's possible that the home page really does have perfect layout stability, and other pages on your website are hurting the origin-level score. I'd suggest testing a few other popular pages to see if the Lighthouse metrics are any different.

In any case, I would highly recommend using the Web Vitals extension for Chrome and browsing your website as a regular user would. It can tell you when your pages have poor CLS in real-time, so you would have a much clearer idea of what is causing the shifts.

Good luck!

Upvotes: 2

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