Short definition

Core Web Vitals — three metrics that measure loading performance, interaction responsiveness, and visual stability: LCP, INP, and CLS.

Also known as: CWV.

Core Web Vitals cover three aspects of the user experience. Largest Contentful Paint measures how quickly the largest content element in the viewport renders, Interaction to Next Paint measures responsiveness to user input, and Cumulative Layout Shift measures unexpected layout shifts.

How are Core Web Vitals measured?

Lab tests help during development, but field data shows what real visitors experience on different devices and connections. Core Web Vitals assessments normally use the 75th percentile of page loads, evaluated separately for mobile and desktop. One slow external widget or heavy image may affect only certain routes, so each page type should be analyzed separately.

What does this mean for a small business?

For small businesses, these metrics are warning signals and a way to prioritize work. An improvement matters when visitors can see key content sooner and interact without buttons shifting around. Do not chase a perfect score at the expense of useful content or a necessary feature.

What should you watch for with Core Web Vitals?

  • measure mobile and desktop separately;
  • review multiple routes and real field data where available;
  • identify what causes slow rendering or delayed interactions instead of looking only at the score;
  • re-measure after each change, not once a year;

How it relates to other website choices

A lean static website or a site built with Astro can reduce browser work and improve these metrics. Caching and a CDN can reduce delivery times. The practical approach is described in Website performance.