Glossary
Core Web Vitals
In short: Core Web Vitals are Google's three user-experience metrics (LCP, INP and CLS) that measure loading speed, responsiveness and visual stability of a page.
Core Web Vitals are the subset of page performance metrics that Google treats as signals of a good page experience and uses in ranking. There are three:
- Largest Contentful Paint (LCP) measures how long the main content takes to appear; the target is 2.5 seconds or under.
- Interaction to Next Paint (INP) measures how quickly the page responds to taps and clicks; the target is 200 milliseconds or under.
- Cumulative Layout Shift (CLS) measures how much the layout jumps around as it loads; the target is 0.1 or under.
Each is assessed at the 75th percentile of real user visits, so a page passes only if most visitors have a good experience, on mobile as well as desktop.
The direct link to AI visibility is indirect but real. Engines with retrieval lean on conventional search results, so a page penalised for poor experience is less likely to be retrieved. Slow or unstable pages also time out or render incompletely for crawlers, which reduces what a model can read.
Seoptist measures Core Web Vitals through the Google PageSpeed Insights API for mobile and desktop, records LCP, INP and CLS over time, and adds the five largest improvement opportunities from each report to your prioritised checklist with a how-to-fix explanation.