Lighthouse and Core Web Vitals

In short: Lighthouse is an auditing tool in Chrome that rates a page’s speed, accessibility, best practices and SEO. The Core Web Vitals are Google’s three most important user-experience metrics.

In more detail: Lighthouse loads a page under simulated conditions (for example a slow mobile network) and awards scores from 0 to 100. The Core Web Vitals are additionally measured on real users and feed into search ranking.

In Depth

• LCP (Largest Contentful Paint): When is the largest visible content there? Goal: under 2.5 seconds.
• INP (Interaction to Next Paint): How fast does the page respond to input? Goal: under 200 ms.
• CLS (Cumulative Layout Shift): Does the layout jump while loading? Goal: under 0.1.
• Typical brakes: Huge images, blocking JavaScript, missing image sizes, slow servers.
• Measuring: Lab data (Lighthouse) helps debugging, field data (CrUX) shows reality.

See also: Search engine optimization (SEO) basics