What Are Core Web Vitals?
Core Web Vitals are a set of three metrics defined by Google to measure the real-world experience of loading and using a web page. Rather than abstract lab scores, they capture what an actual visitor feels: how quickly the main content appears, how fast the page responds when they tap or click, and whether the layout stays stable as it loads.
The three metrics are Largest Contentful Paint (LCP), Interaction to Next Paint (INP) and Cumulative Layout Shift (CLS). LCP measures loading performance, specifically the time taken for the largest visible element, such as a hero image or headline, to render. INP measures responsiveness by recording how long the page takes to react to user interactions across the whole visit. CLS measures visual stability by quantifying how much content unexpectedly shifts around while the page loads.
Google publishes clear thresholds for each. A page is rated good when LCP is 2.5 seconds or less, INP is 200 milliseconds or less, and CLS is 0.1 or less. These targets need to be met for at least 75 percent of real visits, measured using field data from the Chrome User Experience Report rather than a single test.
Why Core Web Vitals Matter
Core Web Vitals matter first because they shape how people experience your site. A page that loads slowly, jumps around as images appear, or freezes when someone taps a button frustrates visitors and pushes them to leave. Better vitals mean lower bounce rates, longer sessions and more conversions, which is why they sit at the heart of good user experience.
They also matter for SEO. Core Web Vitals are part of Google's page experience signals and act as a ranking factor, most noticeably as a tiebreaker between pages of similar relevance and authority. A technically fast, stable page has an advantage over a slower competitor when other ranking factors are close. This is a core part of our SEO work in South Africa and complements broader SEO fundamentals.
How to Improve Core Web Vitals
To improve LCP, optimise and compress your hero images, serve them in modern formats such as WebP, preload key assets, and reduce server response time with caching and a content delivery network. To improve INP, minimise heavy JavaScript, break up long tasks and defer non-essential scripts so the main thread stays free to respond to taps and clicks.
To improve CLS, always set explicit width and height on images and embeds, reserve space for adverts and dynamic content, and avoid inserting elements above existing content after the page has loaded. Measure progress with field data in Google Search Console and lab data in tools like Lighthouse and PageSpeed Insights.
Getting these numbers into the green takes careful technical work. If you would like a hand, fast, stable pages are part of how we build and optimise sites, and clean technical foundations also support AI search optimisation. You can read more in our guides on generative engine optimisation and answer engine optimisation.
What are the three Core Web Vitals?
Core Web Vitals are three metrics Google uses to measure real-world user experience. Largest Contentful Paint (LCP) measures loading: how long until the main content appears, with 2.5 seconds or less considered good. Interaction to Next Paint (INP), which replaced First Input Delay in 2024, measures responsiveness: how quickly the page reacts to taps and clicks, with 200 milliseconds or less good. Cumulative Layout Shift (CLS) measures visual stability: how much the page jumps around as it loads, with a score of 0.1 or less good. Google measures these from real Chrome users, not lab tests.
How to improve Core Web Vitals
To improve LCP, optimise and correctly size images, serve modern formats such as WebP, preload the main image or font, and reduce server response time. To improve INP, minimise heavy JavaScript, break up long tasks, and defer non-essential scripts so the main thread stays free to respond. To improve CLS, set explicit width and height on images and embeds, reserve space for anything that loads late such as ads, and avoid inserting content above existing content. Measure with real-user data in Search Console rather than lab scores alone, because field data is what Google actually uses.
FAQ
What are good Core Web Vitals scores?
Google considers a page good when LCP is 2.5 seconds or less, INP is 200 milliseconds or less, and CLS is 0.1 or less. These thresholds must be met for at least 75 percent of real visits.
Do Core Web Vitals affect SEO rankings?
Yes. Core Web Vitals are part of Google's page experience signals and act as a ranking factor, especially as a tiebreaker between pages of similar relevance. They also affect bounce rate and conversions.
Are Core Web Vitals a ranking factor?
Yes, but a modest one. They are part of Google's page experience signals and act as a tie-breaker between pages of similar relevance and quality. They will not lift weak content, but poor vitals can hold back strong content, so they are worth fixing rather than obsessing over.
What replaced First Input Delay?
Interaction to Next Paint (INP) replaced First Input Delay as a Core Web Vital in March 2024. INP is a more complete measure of responsiveness because it assesses all interactions during a visit, not just the first one.