In Pagespeed insights, I get the following message in Origin Summary: "Over the previous 28-day collection period, the aggregate experience of all pages served from this origin does not pass the Core Web Vitals assessment."
screenshot of the message in PageSpeed Insights
Does anyone know what % of URLs have to pass the test in order to change this? Or what the criteria is?
Lets use Largest Contentful Paint (LCP) as an example.
Firstly, the pass / fail is not based on the percentage of URLs, it is based on the average time / score.
This is an important distinction as you could have 50% of the data fail, but if it only fails by 0.1s (2.6s) and the other 50% of data is passing by 1 second (1.5s) the average will be a pass (average of 2.05s which is a pass).
Obviously this is an over-simplified example but you hopefully get the idea that you could have 50% of your site in the red and still pass in theory, which is why the percentages in each category are more for diagnostics.
If the average time for LCP across all pages in the CrUX dataset is less than 2.5 seconds ("Good") then you will get a green score and that is a pass.
If the time is less than 4 seconds the score will be orange ("Needs improvement") but this will still count as a fail.
Over 4 seconds and it fails and will be red ("Poor").
So you need the following to be true to pass the web vitals (at time of writing):-
If any one of those is over the threshold you will fail, even if the other two are within the green / passes.
FID - when running lighthouse (or Page Speed Insights) on a page you do not get the FID as part of the synthetic test (Lab Data).
Instead you get Total Blocking Time (TBT) - this is a close enough approximation for FID in most circumstances so use that (or run a performance trace).
