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PageSpeed screams about a product photo. Was switching to a new CDN a mistake?

Solvedcore-web-vitalsimageslcp6 replies · 58 views · started
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Accepted solution by Theo Mori — Never lazy load the LCP image. loading="lazy" on an above the fold image delays the request until layout, which pushes LCP back, remove it…
  1. Felix Iqbal
    @patchfiddler

    After switching to a new CDN, our Largest Contentful Paint went from comfortably green to this:

    PageSpeed says the LCP eleemnt is a product photo 🔥 Nothing about it changed visually, same file, same size 🔥 Yet it clearly paints much later now. Im trying to understand what in teh loading order changed. How do u dig into why one specific element is slow? Any advice on how to prove the cause before rolling anything back would help.

    3
  2. Otto Ueda
    @otto_late

    Which LCP sub-part grew teh most: TTFB, load delay, load duration or render delay?

    1 0 helpful
  4. Tariq
    @tariq_uplink

    yeahhh in Chrome DevTools Performance panel, record a page load and look at teh LCP marker. recent versions break LCP into time to first byte, resource load delay, resource load duration and eleemnt render delay. whichever part grew tells you where to look. hope that helps :)

    6 2 helpful
  5. Theo Mori
    @theo.mori
    in reply to @tariq_uplink Accepted solution

    Never lazy-load the LCP image. loading="lazy" on an above-the-fold image delays the request until layout, which pushes LCP back, remove it from the hero image and keep lazy loading for images further down teh page.

    thumbsup

    1 7 helpful
  6. Elena E.
    @eeriksen-1wq

    wait what before micro-tuning, check the image itself. A huge unoptimized file will be slow no matter how early its requested 🤷 right-size and comprses first. idk maybe im wrong lol

    12 0 helpful
  7. Felix Iqbal
    @patchfiddler
    in reply to @theo.mori

    @theo.mori switched the CSS background to a real img with srcset... load delay dropped right away. thanks for explaining teh discovery issue.

    2 0 helpful

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