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I noticed in this Google PSI FAQ written for a previous deprecated version of the test that it says that changes made to the website do no effect the PSI score immediately.

"The speed data shown in PSI is not updated in real-time. The reported metrics reflect the user experience over the trailing thirty days and are updated on a daily basis."

https://developers.google.com/speed/docs/insights/faq

Does this part of the FAQ still apply today? I've noticed that if I reduce the number of DOM elements, the "Avoid an excessive DOM size" complaint in Google PSI immediately shows the correct new count of DOM elements but scores still remain in the same range.

GKGeofferton
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The part you are referring to is "field data", which is indeed still calculated on a trailing 30 day period.

However when you run your website through Page Speed Insights that is tested without any cache and is calculated each time you run it. (known as "Lab Data")

Think of field data as "real world" information, based on visitors to your site and their experiences, it is a far more accurate representation of what is really happening when people visit your site.

Think of the "lab data" as a synthetic test and a diagnostic tool. They try to simulate a slower CPU and a 4G connection but it is still a simulation, it is designed to give you feedback on potential problems. It has the advantage of updating instantly when you make changes though.

For this reason your "field data" will always lag behind your "lab data" when you make changes to the site.

Also bear in mind that some items in the report are purely diagnostics. In your example of "excessive DOM size" this has no direct scoring implications. However it is there to explain why you might be getting slow render times and or a large Cumulative Layout Shift as lots of DOM elements = more rendering time & more chance of a reflow.

See this answer I gave on the new scoring model PSI uses.

GrahamTheDev
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