Yesterday our alarms performance alerts fired because of increased Largest Contentful Paint (LCP) metrics. LCP is one of the Google Web Vitals that will impact SEO ranking. You can read more about how we measure the vitals https://wikitech.wikimedia.org/wiki/Performance/GoogleWebVitals
Largest Contentful Paint
When the banner is pushed the LCP increased in our tests from 1.264 s to 2.789s in our desktop tests.
The Largest Contentful Paint element has a red rectangle.
Before
After
Cumulative Layout Shift
When the banner is pushed the CLS increased from 0.01 to 0.18.
The element that shifted/moved are marked as red.