Why it matters for your business
Core Web Vitals matter for two reasons. First, they are a Google ranking signal, so a slow, unstable page can be held back in search results even when its content is excellent. Second, and more importantly, they reflect how the site actually feels to use. A page that loads slowly or shifts around as it renders frustrates visitors, and frustrated visitors leave before they enquire. Good Core Web Vitals scores protect both your rankings and your conversion rate at the same time.
How it works
The three metrics
Largest Contentful Paint (LCP) measures how long the main content takes to appear, and should be under 2.5 seconds. Interaction to Next Paint (INP) measures how quickly the page responds when someone taps or clicks, and should be under 200 milliseconds. Cumulative Layout Shift (CLS) measures how much the page jumps around as it loads, and should stay under 0.1.
Field data versus lab data
Google bases the ranking signal on field data, which is the real experience of actual visitors, not a one-off lab test. That means a result you see in a speed-testing tool may not match what Google uses. Tools like Search Console and the Chrome User Experience Report show the field data that matters.
Common causes of poor scores
Large unoptimised images, heavy third-party scripts, slow hosting, and images or ads without reserved space are the usual culprits. Most of these are fixable. Compressing images, trimming unnecessary scripts and setting size attributes on media often produces a quick improvement.
A common mistake
A frequent mistake is judging speed only on a fast office connection. The site feels instant on a desktop with fibre, so it is assumed to be fine. But a large share of visitors are on mobile networks, and the same page can be sluggish for them. Always test on a throttled mobile connection, because that is closer to what real customers experience.
