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PageSpeed Insights: Inconsistent result between pages / test runs of the same site (Defer offscreen images)

I'm using an Intersection Observer solution (lozad.js + polyfill) to lazy load images and it's working great. Apart from fact that PSI will not detect it for my start page on Mobile and so I'm stuck at 82-85 but I have 100 for Desktop.

To make it more confusing PSI accepts Defer offscreen images on a subpage that has the exact same lazy load solution.

I'd be very grateful for any input on what could be the cause! Below are some urls if you have a chance to test.

Thanks!

start page (84/100)

https://saprema.se & https://developers.google.com/speed/pagespeed/insights/?url=https%3A%2F%2Fsaprema.se%2F

subpage (93/100)

https://saprema.se/yogabyxor & https://developers.google.com/speed/pagespeed/insights/?url=https%3A%2F%2Fsaprema.se%2Fyogabyxor

Solution

  • Here's what I learned:

    My Mobile test has Field Data but not Desktop so there was a delay from when I made improvements to when my Mobile score reacted. I'm now at a steady 96 / 100 and I'd say it took 4-7 days.

    If you want to get instant feedback, copy your start page to a NOINDEX subpage and run your tests against that url. I haven't tried this but it should be the way to go.