Core Web Vitals are three metrics defined by Google to measure the user experience of a website: Largest Contentful Paint (loading performance), Interaction to Next Paint (responsiveness) and Cumulative Layout Shift (visual stability). They feed into Google's page assessment as part of the page experience signals.
Core Web Vitals are something like an inspection report for your website's user experience: three metrics show how fast a page loads, how quickly it responds to clicks and whether content jumps around while loading. Good scores mean happier visitors – and, as a rule, better chances on Google.
Why do I need Core Web Vitals?
Google evaluates web pages not only by their content but also by the user experience. Core Web Vitals make that experience measurable: Largest Contentful Paint (LCP) measures when the largest visible element has loaded, Interaction to Next Paint (INP) measures how quickly the page responds to clicks and input, and Cumulative Layout Shift (CLS) measures how much content shifts while loading. INP replaced the former First Input Delay metric in March 2024 (Google).
According to Google, the target values are: LCP up to 2.5 seconds, INP up to 200 milliseconds and CLS up to 0.1 – each measured at the 75th percentile of real user data. A distinction is made between lab data (simulated tests, for example with Lighthouse) and field data (measurements from real visitors) – Google's assessment is based on the field data. Our article on Core Web Vitals and PageSpeed shows how to reach these values in practice.
Practical relevance for shop and website owners
For online shops, Core Web Vitals matter twice over: as part of the page experience signals they influence rankings in Google Search, and at the same time they directly affect buying behaviour. Visitors who wait too long for the product image or are irritated by jumping buttons tend to abandon their visit. Slow category and product pages therefore typically cost both visibility and revenue – especially on mobile devices with fluctuating network quality. Professional PageSpeed optimization usually starts with the Core Web Vitals for exactly this reason.
Common mistakes
- Checking lab data only: Lighthouse tests on your own machine are no substitute for field data from real users in the Chrome User Experience Report (CrUX)
- Lazy-loading the LCP element – the largest image does not belong at the end of the loading queue
- Embedding images, banners and ad slots without fixed dimensions, causing layout shifts (CLS)
- Too many third-party scripts (tracking, chat widgets) that degrade responsiveness (INP)
- Optimizing once and never measuring again – new content, plugins and campaigns change the values continuously
What to look out for
Measure regularly with PageSpeed Insights and Google Search Console, both of which evaluate field data from real Chrome users. Prioritize the homepage as well as revenue-critical category and product pages. Common levers are fast hosting, image optimization, caching and reduced JavaScript – our guide Lighthouse 100 for Shopware shows what this looks like in practice. For responsiveness, see our article on optimizing INP. Also note that Google evaluates the values per group of pages with a similar template: a slow category template can affect many pages at once – conversely, a template optimization also benefits all associated pages.
Google does not score the average but the 75th percentile: at least three out of four page views must reach the target value. Individual fast measurements on your own machine therefore say little about the actual rating.