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Glossary Term

Core Web Vitals.

Learn what Core Web Vitals means in modern search and SEO.

Part of speechnounOriginLatin: cor (heart) + Old English: webb (woven thing) + Latin: vitalis (of life)

Google's set of user experience metrics—LCP, INP, and CLS—that measure loading speed, interactivity, and visual stability.

Core Web Vitals are a set of user experience metrics defined by Google as critical indicators of page quality. The three metrics are: Largest Contentful Paint (LCP) — loading performance; Interaction to Next Paint (INP) — interactivity and responsiveness; and Cumulative Layout Shift (CLS) — visual stability. They became an official Google ranking factor in June 2021.

Thresholds and Scoring

Each metric has Good, Needs Improvement, and Poor thresholds: LCP should be under 2.5 seconds; INP should be under 200 milliseconds; CLS should be under 0.1. Scores are measured from real user data (CrUX — Chrome User Experience Report) rather than lab conditions, making them more reflective of actual user experience across devices and connection types.

Improving Core Web Vitals

LCP improvement focuses on optimising the largest visible element (usually a hero image or heading)—through image compression, lazy loading, CDN delivery, and server-side caching. INP improvement requires optimising JavaScript execution and event handlers. CLS improvement involves explicitly sizing images and video elements, avoiding inserting content above existing content, and using CSS transforms instead of layout-triggering properties.

Articles about Core Web Vitals

Read more on the Aergos blog.

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