In short
LCP measures how quickly the main content appears. INP measures how quickly the page responds to interactions. CLS measures whether the layout jumps while the user is trying to read or click.
The numbers matter because they connect SEO with the user experience people feel. A page can look polished and still fail because the main content is late, a click stalls, or the layout shifts under a thumb.
Where it bites
Core Web Vitals bite during paid campaigns, SEO pushes, and relaunches. If performance is measured only after launch, the team finds the regression after users and crawlers already felt it.
What to check
- Which URL templates fail LCP, INP, or CLS on mobile field data?
- Is the LCP element prioritised, sized, and served in the right format?
- Which scripts, embeds, or rendering work block interaction during real user sessions?
Common questions
What are Core Web Vitals?
Core Web Vitals are Google metrics that measure loading speed, responsiveness, and visual stability through LCP, INP, and CLS.
Do Core Web Vitals affect SEO?
Yes. Google uses them as a page experience signal, and they often correlate with conversion because slow or unstable pages make tasks harder.
What should you check first for Core Web Vitals?
Start with mobile field data, the LCP element, third-party scripts, image delivery, layout stability, and whether the slow templates match valuable SEO or conversion pages.