Core Web Vitals put a number on how a page feels to a real visitor: how fast it loads, how quickly it responds, and how stable it is while loading. Google measures these from real user data and factors page experience into ranking, so they sit at the intersection of SEO and user experience.
What Are the Three Core Web Vitals?
According to Google's web.dev guidance, each metric has a defined good threshold, measured at the 75th percentile of real users:
- Largest Contentful Paint (LCP): loading. Good is 2.5 seconds or less. It measures how long the largest visible element takes to render.
- Interaction to Next Paint (INP): responsiveness. Good is 200 milliseconds or less. It measures how quickly the page responds to user interactions across the whole visit.
- Cumulative Layout Shift (CLS): visual stability. Good is 0.1 or less. It measures how much the layout shifts unexpectedly as the page loads.
INP replaced First Input Delay (FID) as a Core Web Vital in March 2024, because it captures responsiveness across the entire interaction, not just the first tap.
How Do You Optimize Each Metric?
- Improve LCP: serve a fast server response, compress and properly size images, preload the main image or font, and remove render-blocking resources.
- Improve INP: reduce heavy JavaScript, break up long tasks, and defer non-essential scripts so the main thread can respond to input quickly.
- Improve CLS: set explicit width and height on images and embeds, reserve space for ads and banners, and avoid inserting content above what the user is already reading.
How Do You Measure Core Web Vitals?
There are two kinds of data. Field data is what Google actually uses for ranking: real measurements from Chrome users, visible in Google Search Console and the Chrome User Experience Report. Lab data comes from tools like PageSpeed Insights and Lighthouse, which simulate a load and are useful for debugging. Always confirm a fix against field data, since a page can score well in the lab but fail for real users.
Do Core Web Vitals Affect Rankings?
Yes, but as one factor among many. Google has said page experience, including Core Web Vitals, is a ranking signal, and it works as a tiebreaker rather than an override: great vitals will not rank thin content, but among comparable pages, a better experience can help. The stronger reason to fix them is conversion, since slow, unstable pages lose buyers regardless of ranking.
Frequently asked questions
What are the three Core Web Vitals?+
They are Largest Contentful Paint (LCP) for loading, with a good threshold of 2.5 seconds or less; Interaction to Next Paint (INP) for responsiveness, at 200 milliseconds or less; and Cumulative Layout Shift (CLS) for visual stability, at 0.1 or less, measured at the 75th percentile of real users.
What replaced FID in Core Web Vitals?+
Interaction to Next Paint (INP) replaced First Input Delay (FID) in March 2024. INP measures responsiveness across the entire visit rather than only the first interaction, giving a fuller picture of how a page responds to users.
Do Core Web Vitals help SEO?+
Yes, as part of Google's page experience signals, but as one factor among many rather than an override. Good vitals will not rank weak content, though among similar pages a better experience can help, and it also lifts conversion.