Core Web Vitals are a set of metrics introduced by Google to measure the real-world experience of using a website. They're not just technical benchmarks – they directly affect where your site ranks in search results.
The three metrics that matter
LCP (Largest Contentful Paint) – how long it takes for the main content (usually a large image or headline) to appear on screen. Google's threshold: under 2.5 seconds.
INP (Interaction to Next Paint) – how quickly the page responds when a user clicks a button, taps a link, or interacts in any way. This replaced the older FID metric. Threshold: under 200ms.
CLS (Cumulative Layout Shift) – how much the layout jumps around as the page loads. Elements that shift unexpectedly (like a button moving just as you're about to tap it) create a frustrating experience. Threshold: score under 0.1.
Why they affect rankings
Google uses Core Web Vitals as a ranking signal. Two sites with equally good content will see the faster, more stable one rank higher. For a business that relies on Google traffic, this is a direct commercial factor.
What causes poor scores
Unoptimised images, too many JavaScript files, fonts loaded in a way that blocks rendering, missing size attributes on images – all common issues, especially on WordPress sites with many plugins. Clean hand-coded sites typically score much better here from day one.