Core Web Vitals explained: what LCP, INP and CLS mean (+ thresholds)

Google measures how your pages feel to real visitors using three numbers called Core Web Vitals. They affect rankings, but more importantly they reflect whether visitors stay or leave.

The 3 types of Core Web Vitals

There are three Core Web Vitals, each measuring one part of how a page feels to a visitor:

• LCP (Largest Contentful Paint): loading. How fast the main content appears.
• INP (Interaction to Next Paint): responsiveness. How fast the page reacts to taps and clicks. It replaced FID in March 2024.
• CLS (Cumulative Layout Shift): visual stability. How much the layout jumps while loading.

What is LCP in Core Web Vitals?

Largest Contentful Paint is the time until the biggest thing on screen, usually a hero image or headline, is visible. Google wants it under 2.5 seconds. Common causes of slow LCP are huge images, slow servers and scripts that block the page.

What is CLS in Core Web Vitals?

Cumulative Layout Shift measures how much content moves while loading. You’ve felt it when you try to tap a button and an ad pushes it down. Google wants it under 0.1. It’s usually fixed by reserving space for images, embeds and banners.

What is INP in Core Web Vitals?

Interaction to Next Paint measures how quickly the page reacts when someone taps or clicks. Google wants it under 200 milliseconds. Heavy JavaScript, chat widgets and tracking scripts are the usual culprits.

Core Web Vitals thresholds (good, needs improvement, poor)

These are Google’s official limits. A page passes when at least 75% of real visits (the 75th percentile) are in the “good” range, measured separately for mobile and desktop.

• LCP: good at 2.5 s or less, needs improvement up to 4 s, poor above 4 s
• INP: good at 200 ms or less, needs improvement up to 500 ms, poor above 500 ms
• CLS: good at 0.1 or less, needs improvement up to 0.25, poor above 0.25

Check yours in two minutes

• Open PageSpeed Insights and paste your URL
• Look at the mobile tab first; that’s what most visitors use
• Real-user data at the top matters more than the lab score
• In Google Search Console, the Core Web Vitals report shows which pages fail

What a fix looks like

On one sales page I took LCP from 11.6s to 2.2s without changing the design, mostly by fixing how the hero image and third-party scripts loaded. Most sites have two or three issues causing most of the slowness.