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https://developers.google.com/speed/pagespeed/insights/

On 27th May 2020 I had used page speed where I got a pretty good score for desktop (90+) and for mobile around (85+), but as on 28th May 2020 the metrics seems to drastically changed, I can see the PageSpeed has new version (v6) but no proper release notes are provided here https://developers.google.com/speed/docs/insights/release_notes.

Anyone had faced similar issue and found that google pagespeed did undergo certain upgrades then please provide me some references if possible.

Sagar
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  • PSI still uses version 5, are you testing through webpagetest.org as that is the only reference I can find to v6 and if so what settings did you use. – GrahamTheDev May 28 '20 at 10:24
  • @GrahamRitchie, No I am using https://developers.google.com/speed/pagespeed/insights/ I found a post about this looks like got what I was looking for https://web.dev/lighthouse-whats-new-6.0/ Thanks for a prompt reply – Sagar May 28 '20 at 11:01
  • ahhh just answered, have deleted my answer. PSI website still uses v5 and the v6 API is not available yet, my score dropped too due to their focus on Total Blocking Time and Largest Contentful Paint when I tested through webpagetest.org. – GrahamTheDev May 28 '20 at 11:05
  • undeleted my answer as there were a lot of answers being added that did not answer this question, I will add in the link you have @sagar10 – GrahamTheDev May 28 '20 at 17:26

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After some digging I managed to find the draft of the proposed scoring weights.

https://web.dev/performance-scoring/?utm_source=lighthouse&utm_medium=wpt

The large shift in scores is down to how the weightings have changed

Lighthouse v6

  • First Contentful Paint 15%
  • Speed Index 15%
  • Largest Contentful Paint 25%
  • Time to Interactive 15%
  • Total Blocking Time 25%
  • Cumulative Layout Shift 5%

Lighthouse v5

  • First Contentful Paint 20%
  • Speed Index 27%
  • First Meaningful Paint 7%
  • Time to Interactive 33%

As you can see there is a massive shift to emphasis on Total Blocking Time (TBT) (JavaScript execution time mainly) and when the Largest Contentful Paint (LCP) occurs (presumably as this indicates large shifts in the page layout / visible content that may be distracting / is a good indicator of when the above the fold content is fully loaded (as opposed to showing a 'spinner')).

They have also added a third new metric Cumulative Layout Shift (CLS), a metric that works out how much the page layout 'moves around'. This has a low weighting at the moment but I imagine it is part of a larger plan to ensure all late-loading assets are captured that affect the 'above the fold' content and may cause frustration (trying to click a link to find an advert loaded in and moved it for example).

These huge changes in weightings and introduction of new metrics are the cause of massive score decreases you may experience.

I can confirm that my site that used to score 99 or 100 now only scores 87 so it is indeed a large shift in how they are scoring. They also now seem to take into account SVG rendering as my site is 100% SVG driven yet scores low on the LCP, this is something they did not initially take into account with the LCP stats.

For now focus on the two articles I linked on TBT and LCP as those are the new metrics they are choosing to emphasise making up 50% of your score.

Update

As OP pointed out in the comments the main changes for the new PSI v6 are located here

Community
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GrahamTheDev
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    Thank you so much for sharing, I just spent the last two hours trying to figure out why our metrics had dropped for certain pages. #Google It's messed up that PSI didn't update the release notes. – Mike Hemelberg Jun 01 '20 at 22:09
  • Yeah I was glad OP asked this question as I had loads of sites that dropped. Luckily we had the same rendering problem across all of them so it was easy to fix and now they all back at 100 / 100 :-). Google don't seem to realise how much some people rely on this tool as there was no real announcement of a version 6 and the GitHub repository didn't release a new version update for some reason. – GrahamTheDev Jun 08 '20 at 15:41