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core-web-vitalscumulative-layout-shiftweb-vitals

Field CLS report very good on GA but bad on Search Console. What should I do to fix it?

On search console, it says some of my links have bad CLS.

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However, I've been tracking the links for a while and the CLS is perfect (the value is 1000x bigger, according to how the web-vitals client tracks it).

I am using this official library to track the metrics.

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Is there anything else I can try?

Solution

  • The Chrome User Experience Report (CrUX) that powers the Core Web Vitals program is collected from real users, but is a lower-level API run in the Chrome Browser that has has access to the full page information.

    In contrast JavaScript APIs (as used by RUM solutions - including the web-vitals library) have a more limited view due to security restrictions of web APIs.

    This can lead to a number of differences, in particular for any iframes that impact the CWVs as Web APIs cannot peer into iframes to get those details.

    However, the user won’t know these are iframes (unless they’re a web developer and go looking!) so they do count as the user experience of the top-level page and hence why CrUX measure them.

    This is just a limitation unfortunately for good security reasons.

    Does your web page have iframes? Either for other pages on your site, or by embedding third-party content like videos?