What Are Core Web Vitals?

Core Web Vitals are a set of user-centred performance metrics defined by Google. They measure how fast, stable, and responsive a page feels from a real user's perspective — not just how quickly the server responds.

They directly influence your Google Search ranking. More importantly, they reflect the actual experience your users have.

LCP — Largest Contentful Paint

LCP measures how long it takes for the largest visible element on the page to fully render.

Good: under 2.5 seconds

Needs improvement: 2.5–4 seconds

Poor: over 4 seconds

How to improve it: Preload your hero image, use a CDN, avoid render-blocking scripts, and serve next-gen image formats.

CLS — Cumulative Layout Shift

CLS measures visual instability — how much page elements move around unexpectedly as the page loads.

Good: under 0.1

Needs improvement: 0.1–0.25

Poor: over 0.25

How to improve it: Always set explicit width and height on images and embeds. Reserve space for ads and dynamic content.

INP — Interaction to Next Paint

INP replaced FID in 2024. It measures the delay between a user interaction and when the browser visually responds.

Good: under 200ms

Needs improvement: 200–500ms

Poor: over 500ms

How to improve it: Minimize JavaScript execution on the main thread, break up long tasks, use web workers for heavy computation.

How to Measure

Use Google Search Console for real-world field data, and PageSpeed Insights or Lighthouse for lab data. Track all three. Improve the worst one first.