CODEWITHSUNDEEP
google-search-consolelighthousepagespeed-insightsweb-performancecore-web-vitals
addyo
addyo

Reputation: 2938

Why does Cumulative Layout Shift differ between PageSpeed Insights and Search Console?

Why does the Cumulative Layout Shift metric reported in Google's speed measurement tools, like Lighthouse/PageSpeed Insights differ from what is reported in Search Console?

Upvotes: 6

Views: 1981

Answers (1)

addyo
addyo

Reputation: 2938

There is some nuance to how PageSpeed Insights (PSI) and Search Console report on Cumulative Layout Shift. The lab portion (Lighthouse) of PSI measures CLS until Lighthouse considers a page fully loaded. It does not measure beyond page-load.

enter image description here

Search Console and the field portion of the PSI uses Chrome User Experience Report data and measures CLS until unload, stopping reporting after pagehidden (i.e this is inclusive of CLS beyond page-load). What this means is that the reporting you see in different tools can vary based on the window of time we are able to look at.

enter image description here

Lab tools like Lighthouse have to define a shorter window because they are focused on the experience during page load and optimize for delivering information about the experience quickly. Field data is able to take a more holistic view of the user-experience, which could include shifts caused after a page has loaded and the user has scrolled down to other interactions contributing to CLS.

Upvotes: 3

Related Questions