First Contentful Paint (FCP)

• time until any part of the page's content is rendered
• target <1.8s

Largest Contentful Paint (LCP)

• moment at which the largest DOM object in the viewport is rendered
• measures loading performance
• target <2.5s

First Input Delay (FID)

• time between user's first interaction and browser's response
• measures interactivity
• target <100ms

Cumulative Layout Shift (CLS)

• visual stability of a page
• affected by dynamically loaded content (like third party ads)
• starts at 0, target <0.1

Testing

• use the Lighthouse tool in Chromium to measure