Glossary
Core Web Vitals
Core Web Vitals are three measurements Google uses to describe how a page feels to visitors: how fast the main content loads (LCP), how quickly the page responds to input (INP) and how stable the layout is while it loads (CLS). Each has a published threshold for a good score.
The three metrics
- Largest Contentful Paint (LCP) measures loading. Good is 2.5 seconds or less. Poor is more than 4 seconds.
- Interaction to Next Paint (INP) measures responsiveness. Good is 200 milliseconds or less. Poor is more than 500 milliseconds. INP replaced First Input Delay as a Core Web Vital in 2024.
- Cumulative Layout Shift (CLS) measures visual stability. Good is a score of 0.1 or less. Poor is more than 0.25.
Anything between good and poor is rated "needs improvement". A page passes when it meets the good threshold for all three at the 75th percentile of page loads, with mobile and desktop assessed separately. The thresholds are published by Google at web.dev.
Why it matters to a business website
These numbers describe things visitors notice: a page that takes too long to show its main content, a button that does not react, or text that jumps as an image loads above it.
They also matter for search. Google's documentation recommends that site owners achieve good Core Web Vitals for success with Search, and describes them as part of the page experience that its core ranking systems seek to reward. Stryx treats them as one part of a site's quality, not as a shortcut to rankings.