Core Web Vitals

The three metrics and their thresholds

• LCP (Largest Contentful Paint) — render time of the largest element; a good score is ≤ 2.5 s.
• INP (Interaction to Next Paint) — latency of responses to interactions; a good score is ≤ 200 ms.
• CLS (Cumulative Layout Shift) — the sum of unexpected layout shifts; a good score is ≤ 0.1.

Why it matters

Core Web Vitals tie user experience to search visibility: slow, unstable pages lose both conversions and rankings. Google research shows that meeting CWV thresholds significantly reduces page-load abandonment rates.

Example

A page "passes" a metric when the 75th percentile of visits falls within the good threshold — e.g. an LCP of 2.1 s at p75 is a pass, even if individual visits are slower.

Metric   Good           Needs improvement   Poor
──────────────────────────────────────────────────────
LCP      ≤ 2.5 s        2.5 – 4.0 s           > 4.0 s
INP      ≤ 200 ms       200 – 500 ms          > 500 ms
CLS      ≤ 0.1          0.1 – 0.25            > 0.25

What is the difference between field data and lab data?

Field data (e.g. CrUX) comes from real users and determines the Core Web Vitals assessment. Lab data (e.g. Lighthouse) is produced in a controlled environment and is used for diagnosis and debugging.