Core Web Vitals, are three metrics that score a user's experience loading a webpage.

Google specifies three Core Web Vitals

• Largest Contentful Paint (LCP)
• First Input Delay (FID)
• Cumulative Layout Shift (CLS)

These metrics show how your pages perform, based on real world usage data. Core Web Vitals are a subset of factors that will be part of Google’s “page experience” score.

Core Web Vitals metrics show:

• how quickly page content loads.
• how quickly after a browser loaded a webpage can respond to a user's input.
• how unstable the content (shifting items) is as the browser is loading the web page.

Metric | Good | Needs improvement | Poor

• LCP | <=2.5s | <=4s | >4s
• FID | <=100ms | <=300ms | >300ms
• CLS | <=0.1 | <=0.25 | >0.25