What is Core Web Vitals?

Core Web Vitals were introduced by Google in 2021 as official ranking factors. They measure three distinct aspects of the user experience: loading speed, interactivity, and visual stability.

Largest Contentful Paint (LCP) measures how quickly the largest visible element, usually a hero image or heading, appears. Good LCP is under 2.5 seconds. Poor LCP is over 4 seconds. This is the metric most affected by large unoptimized images and slow server response times.

Interaction to Next Paint (INP) measures how quickly the page responds after a user click or tap. Good INP is under 200ms. Poor INP is over 500ms. This is affected by heavy JavaScript that blocks the main thread.

Cumulative Layout Shift (CLS) measures how much the visible page elements move unexpectedly during loading, like a button that shifts just as you are about to click it. Good CLS is under 0.1. This is caused by images without specified dimensions, fonts that swap in during load, and dynamic content injections.

Google measures Core Web Vitals using real-world user data collected through Chrome (called field data) and also through lab testing tools like PageSpeed Insights and Lighthouse. Sites that pass Core Web Vitals thresholds get a small but meaningful ranking boost, particularly in mobile search.

DIY website builders struggle with Core Web Vitals because their architectures are not optimized for these metrics, they load heavy JavaScript frameworks to power their editors, which hurts INP and LCP. Custom-coded sites can be built specifically to hit good scores on all three metrics through image optimization, minimal JavaScript, and pre-rendered HTML.

Checking your Core Web Vitals is free: enter your URL in Google PageSpeed Insights or check the Core Web Vitals report in Google Search Console.

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