Core Web Vitals explained simply: LCP, INP and CLS

Core Web Vitals are three metrics Google uses to judge a page's actual user experience: LCP measures loading speed, INP measures how quickly the page responds to interaction, and CLS measures visual stability while loading. Good thresholds are LCP up to 2.5 seconds, INP up to 200 milliseconds and CLS up to 0.1. You measure them via Search Console or PageSpeed Insights.

What the three metrics measure

LCP: Largest Contentful Paint

LCP measures how long it takes for the largest visible element on a page to load, usually an image or a large block of text. It stands for the feeling that the page has arrived. A good LCP is up to 2.5 seconds. Common causes of a poor score are large, uncompressed images, a slow server or scripts that block loading.

INP: Interaction to Next Paint

INP measures how quickly a page responds to an interaction, such as a click on a button or a menu. It has replaced the earlier First Input Delay (FID) as the official Core Web Vital since March 2024, because it measures the whole interaction rather than just the first response. A good INP is up to 200 milliseconds. Sluggish INP scores are usually caused by too much JavaScript running in the background and blocking the browser.

CLS: Cumulative Layout Shift

CLS measures how much elements on a page still move after becoming visible, for example when an image without a fixed size loads late and pushes the text below it down. A good CLS is up to 0.1. The usual causes are images or ad slots without reserved space, and fonts that change line breaks as they load.

How much Core Web Vitals matter for ranking

Core Web Vitals are part of what Google calls page experience signals and do feed into ranking, but as one criterion among many and with limited weight. Relevance, content and authority weigh considerably more. In practice, the metrics work mostly as a tiebreaker: between two pages of similar content quality, the technically faster one can edge ahead. Anyone expecting to rank noticeably higher through better scores alone will usually be disappointed. Still, the work pays off, because a fast, stable page loses fewer visitors before they have read anything at all.

How to check your scores

The most reliable place is the Core Web Vitals report in Google Search Console. It shows real measurements from your actual visitors, split by mobile and desktop, and flags pages as good, needs improvement or poor. For a quick check of individual pages, PageSpeed Insights works well: it delivers lab data from a simulated test run immediately and, once enough real traffic exists, adds real user data from the same dataset Search Console draws on.

Where Core Web Vitals fit into the bigger picture

Core Web Vitals are one part of the technical check in an SEO audit and one of the points a SEO consultant keeps an eye on continuously. If you want to improve your own scores, the best place to start is images and scripts: compressed, correctly sized images and less blocking JavaScript solve a large share of the most common problems.