Core Web Vitals: what LCP, INP and CLS mean, and how to pass

Core Web Vitals are Google’s three page-experience metrics, measured on real visitors: LCP (Largest Contentful Paint) should be 2.5 seconds or less, INP (Interaction to Next Paint) 200 milliseconds or less, and CLS (Cumulative Layout Shift) 0.1 or less, for at least 75% of visits. Check them in PageSpeed Insights or Search Console, and fix mobile first.

By Hassan Rawther, Founder, Unlearn Academy · Reviewed 21 October 2026

The slider that cost a clinic its mobile visitors

A Thrissur clinic’s homepage opened with a 4-image slider. On mobile, LCP was 5.8 seconds and CLS jumped as banners loaded.

We replaced the slider with one compressed image, set image sizes and moved a chat widget to load later.

LCP dropped to 2.1 seconds and CLS to 0.03. Bounce rate fell and form submissions from mobile rose by a third.

Illustrative example based on a common pattern in Kerala e-commerce accounts. Numbers rounded.

What Core Web Vitals measure

LCP measures how long the main content takes to appear. INP measures how quickly the page responds to taps and clicks (it replaced FID in 2024). CLS measures how much the layout jumps around.

Google uses real-user data (field data) from Chrome, at the 75th percentile, mainly from mobile. Lab tests help find causes; field data decides pass or fail.

Good: LCP ≤ 2.5 s · INP ≤ 200 ms · CLS ≤ 0.1 (75% of visits)

Check your Core Web Vitals

LCP
Needs improvement
INP
Good
CLS
Needs improvement

The page doesn’t pass yet. Fix LCP, CLS first. LCP: compress the hero image and remove sliders. INP: cut heavy scripts and plugins. CLS: set image sizes and reserve space for banners.

Want a second opinion on your numbers? Join the community and post them for doubt-clearing.

Common causes of failing scores

ProblemUsual cause
LCP: slowLarge hero images, sliders, slow hosting
INP: slowHeavy JavaScript, too many plugins, chat widgets
CLS: jumpyImages without sizes, late banners and ads

How experienced marketers use Core Web Vitals

  1. 1. Prioritise speed work

    Fix the metric that fails on your most important templates first.

  2. 2. Brief developers

    Field data from Search Console shows which URL groups fail.

  3. 3. Protect conversions

    Faster, stable pages usually convert better on mobile data.

What good looks like

Business typeStarting ruleWhy
LCP≤ 2.5 s good, > 4 s poorGoogle’s thresholds.
INP≤ 200 ms good, > 500 ms poorReplaced FID in March 2024.
CLS≤ 0.1 good, > 0.25 poorUnitless score.

When the number lies

Lab vs field
A great lab score doesn’t guarantee passing field data, and vice versa.
Low-traffic pages
Pages without enough Chrome data show only lab results or URL-group data.

Mistakes to avoid

  • Testing only on desktop

    Mobile users, most of your traffic, get the slow experience.

  • Chasing a 100 score

    Time spent on diminishing returns instead of conversions.

  • Adding plugins to fix speed

    More scripts, often worse INP.

Related terms

Questions people ask about Core Web Vitals

What are Core Web Vitals?

Three metrics Google uses to measure page experience: LCP for loading, INP for responsiveness and CLS for visual stability.

Are Core Web Vitals a ranking factor?

They are part of Google’s page experience signals. Relevance and content matter more, but poor vitals can hold a page back and hurt conversions.

How do I check Core Web Vitals?

PageSpeed Insights for a single URL, and Search Console’s Core Web Vitals report for the whole site.

What replaced FID?

INP (Interaction to Next Paint) replaced FID as a Core Web Vital in March 2024.

Put it into practice

Join our community

Prefer to talk first? Book a free counselling call.