Core Web Vitals are user-experience metrics. They are useful performance signals, but improving a Lighthouse score is not the same thing as guaranteeing better search rankings.
LCP — Largest Contentful Paint
LCP measures when the largest relevant content element becomes visible. Large images, slow servers, render-blocking resources and client-side rendering can all contribute to poor LCP.
INP — Interaction to Next Paint
INP measures responsiveness to user interactions. Long JavaScript tasks can prevent the browser responding promptly after a click, tap or keyboard action.
CLS — Cumulative Layout Shift
CLS measures unexpected movement of page content. Reserve space for images and embeds and avoid inserting content above existing content unexpectedly.
Lab versus field data
Lab tests use controlled conditions; field data reflects real users and varies by device, connection and geography. Treat them as complementary.
Practical optimisation
- Measure before changing code.
- Optimise large above-the-fold resources.
- Reduce unnecessary JavaScript work.
- Reserve dimensions for images and embeds.
- Cache and compress static assets appropriately.
- Retest mobile and desktop after changes.
Ingenix's SEO Checker includes Lighthouse performance information alongside its SEO audit.