Core Web Vitals
Core Web Vitals are three metrics that Google uses to describe how fast and stable a page feels to real visitors. Unlike previous metrics, they are not measured in a lab, but based on actual page views.
LCP (Largest Contentful Paint) measures when the largest visible element loads, usually the hero image or headline. A good value is up to 2,5 seconds. INP (Interaction to Next Paint) measures the response to clicks and input; a good value is up to 200 milliseconds. CLS (Cumulative Layout Shift) measures how much the layout jumps during loading; a good value is below 0,1.
A real-world example: A page loads a 3-megabyte hero image as a JPEG. This alone pushes the LCP (Low Completion Point) to over four seconds. The same image as a 180-kilobyte WebP image brings it down to under two seconds. The second most common mistake is images without size information: The text shifts downwards during loading, the CLS (Close Completion Point) increases, and the visitor clicks on the wrong image.
You can see your own metrics in the Search Console under Core Web Vitals, which uses real user data from the last 28 days.
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