Difference scores in Core Web Vitals

  • Resolved bobsled

    (@bobsled)


    3 years, 8 months ago

    I don’t want to pester you @isaumya

    But I have one question that you might be able to help me with.

    When I bypass the cache using Development Mode, my Core Web Vitals results are a lot better in PageSpeed Insights.

    For instance, Largest Contentful Paint is 2.4 sec with the cache but goes down to 1.9 sec with the dynamic cache in Dev Mode.

    First Contentful Paint drops from 1.7 to 1.4 sec, and Speed Index from 2.1 down to 1.9.

    Cumulative Layout Shift and Time To Interactive are about the same.

    I’ve tested over 20 pages, and the results are always very similar.

    Of course, in Dev Mode, my TTFB increases from 40-50 ms up to 600-700 ms.

    Do you know what causes this discrepancy?

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  • Plugin Contributor iSaumya

    (@isaumya)

    Hard to say but inside page speed insight when you test a URL, you get the lab data which is kind of simulated data and not the actual field data that Google uses which is gathered from actual users.

    The lab data fluctuate a lot. You should always look at your field data. Even in Cloudflare if you go under the speed section there is a section for browser insight that checks the core web vitals real-time for actual users. I think there you will get a much accurate representation than the page speed insight lab data.

    Thread Starter bobsled

    (@bobsled)

    Okay. Thanks very much, @isaumya

    I’ll check that Cloudflare data.

Viewing 2 replies - 1 through 2 (of 2 total)
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