Core Web Vitals are Google's metrics for loading speed, responsiveness and visual stability of a page. They're assessed from real user experience and from lab tests.
What Core Web Vitals measure
- LCP: the main content should render within 2.5 seconds.
- INP: the response to an interaction should come within 200 milliseconds.
- CLS: the sum of unexpected layout shifts should be 0.1 or less.
Field assessment uses the 75th percentile of visits. That's why a one-off Lighthouse test may not match what real users experience.
How much it decides
Core Web Vitals are part of a broader page experience assessment. They're not the main lever, and they won't make up for weak relevance, thin content, missing links or broken indexing.
Why fix them anyway
A slow or unstable page makes the site harder to use and can hurt conversions. Optimization has business value even when rankings don't visibly move.
Set priorities by field data, by how important the template is and by the actual problem. You don't need to chase a score of 100 if users already hit the good thresholds and other bugs have a bigger impact.