Google wants to know what a website feels like for real people. To find out, it uses anonymised measurement data from the Chrome browser. Three values are measured:
- LCP (Largest Contentful Paint) measures when the largest visible piece of content has loaded, such as the hero image. Good means 2.5 seconds or less.
- INP (Interaction to Next Paint) measures how quickly the page responds to clicks, taps and input. Good means 200 milliseconds or less. INP replaced the older FID metric in March 2024.
- CLS (Cumulative Layout Shift) measures how much content jumps around while the page loads. Good means a score of 0.1 or less.
The rating isn't based on a single visit. A page counts as good if at least 75% of page views stay within the limit, measured separately for mobile and desktop. Because this is real-world data, older phones and weak mobile connections count too.
For a business, the values matter for two reasons. Google uses them in its ranking systems. Good scores alone won't get you to the top, though: content is still what counts. The second reason matters more: a slow or jumpy page is annoying. Anyone who goes to tap “Call” and misses because a banner loads in late is quickly gone.
What to look out for: typical culprits are oversized images, lots of fonts, heavy plugins and third-party scripts. Images without a fixed size and banners that appear late make the layout jump. You can check the values for free with PageSpeed Insights or in Google Search Console.
Good Core Web Vitals are the goal for every website we build, which is why we optimise images and keep the code lean.
A hotel on Lake Lucerne shows a large, uncompressed panorama photo on its homepage. On a phone it only appears after several seconds, and the LCP is well over the limit. On top of that, a late-loading cookie banner pushes the booking button down. Anyone who was about to tap it misses. After the rework, the photo is compressed and saved in the modern WebP format. The banner has a fixed spot and no longer moves anything. A few weeks later, PageSpeed Insights shows green scores, and booking on a phone works without any mis-taps.