Core Web Vitals: why website speed matters
LCP, INP and CLS are the three metrics Google uses to measure user experience. We explain what they mean, what good values are and how to improve them.
Core Web Vitals are a set of metrics Google uses to assess how users experience a page’s speed and stability. They are one of the signals used to evaluate page experience – and, more importantly, they directly affect whether a visitor stays or goes back to the search results.
The three key metrics
- LCP (Largest Contentful Paint) – time until the largest visible element is rendered. Good: up to 2.5 s.
- INP (Interaction to Next Paint) – how quickly the page responds to clicks and taps. It replaced FID in March 2024. Good: up to 200 ms.
- CLS (Cumulative Layout Shift) – how much elements jump around while loading. Good: up to 0.1.
How to improve them
- Serve images in modern formats (WebP, AVIF), sized for the screen.
- Set image dimensions (
widthandheight) so the browser reserves space. - Lazy-load images below the fold with
loading="lazy". - Limit third-party scripts – every widget, chat or tracker slows the page down.
- Enable server-side compression and caching.
- Avoid heavy libraries where a few lines of CSS or JavaScript will do.
How to check
Use PageSpeed Insights or the Core Web Vitals report in Google Search Console, which shows data from real users.
Our new website was built on exactly these principles. If your site is slow, we can take care of it.