Core Web Vitals 2025 — How to Improve Your Scores and Rank Higher on Google

Since 2021, Google has officially included Core Web Vitals in its search rankings. A slow site = a lower position. But what exactly should you measure and how do you fix it? Here's the complete guide.

What Are Core Web Vitals?

Core Web Vitals (CWV) are a set of metrics measuring the user experience on a webpage. Google uses them as a ranking signal as part of Page Experience.

Three main metrics:

1. LCP (Largest Contentful Paint) — time to render the largest element on the page
2. INP (Interaction to Next Paint) — responsiveness to user interactions
3. CLS (Cumulative Layout Shift) — layout stability (do elements "jump" around?)

LCP — Largest Contentful Paint

What Does It Measure?

The time from page load to the rendering of the largest visible element (typically a hero image, hero text, or banner).

Thresholds:

• ✅ Good: < 2.5 seconds
• ⚠️ Needs improvement: 2.5 – 4 seconds
• ❌ Poor: > 4 seconds

How to Improve LCP?

1. Preload critical resources

<link rel="preload" href="/en/hero.webp" as="image" fetchpriority="high">

2. Optimise images

• Convert to AVIF or WebP (50–80% smaller file size)
• Use appropriate sizes (srcset, sizes)
• Never load 2000px-wide images when they display at 400px

3. Eliminate render-blocking resources

• Critical CSS inline, the rest loaded asynchronously
• JavaScript asynchronous (async, defer)
• Fonts preloaded with font-display: swap

4. Preconnect to external domains

<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="dns-prefetch" href="https://www.googletagmanager.com">

5. Use a CDN Serve static assets from a CDN close to the user. For Europe — a server in Western Europe.

INP — Interaction to Next Paint

What Does It Measure?

The time from a user interaction (click, touch, keyboard) to the rendering of a visual response on screen.

Replaced FID (First Input Delay) in March 2024.

Thresholds:

• ✅ Good: < 200 ms
• ⚠️ Needs improvement: 200 – 500 ms
• ❌ Poor: > 500 ms

How to Improve INP?

1. Reduce long JavaScript tasks Tasks blocking the main thread for > 50ms are the main culprit. Break them into smaller pieces using scheduler.yield() or setTimeout(0).

2. Defer non-critical JavaScript Analytics, chat widgets, social media widgets — load them after interaction or at idle:

window.addEventListener('load', () => {
  requestIdleCallback(() => loadThirdParty())
})

3. Use web workers Move heavy computations (sorting, filtering large lists) to a web worker — doesn't block the UI.

4. Virtualise long lists A list of 10,000 products in the DOM is a disaster. Render only visible elements (react-window, tanstack-virtual).

CLS — Cumulative Layout Shift

What Does It Measure?

The sum of all unexpected layout shifts during page load.

Thresholds:

• ✅ Good: < 0.1
• ⚠️ Needs improvement: 0.1 – 0.25
• ❌ Poor: > 0.25

How to Improve CLS?

1. Always set width and height on images

<!-- Bad -->
<img src="hero.jpg" alt="Hero">

<!-- Good -->
<img src="hero.jpg" alt="Hero" width="800" height="600">

The browser reserves space before the image loads.

2. Reserve space for ads and embeds

.ad-container { min-height: 250px; }

3. Avoid dynamically inserting content above the fold Cookie banners, notifications, promotional banners — they should appear at the bottom or push content down from the top.

4. Use font-display: optional or preload fonts Font swapping can cause CLS when the font loads late and changes text metrics.

Tools for Measuring Core Web Vitals

1. PageSpeed Insights (PSI)

pagespeed.web.dev — free, gives both lab data and real user data from Chrome (CrUX).

2. Google Search Console

The "Core Web Vitals" report shows data from real users of your site. Important: PSI covers one URL, Search Console covers your entire site.

3. Lighthouse

Built into Chrome DevTools (F12 → Lighthouse). Great for quick analysis.

4. WebPageTest

webpagetest.org — more detailed waterfall, recording filmstrip, multiple server locations.

5. CrUX Dashboard (Looker Studio)

A free Google template for tracking CWV trends over time for your domain.

Typical Results Before and After Optimisation

Example e-commerce project (WooCommerce):

Optimisation time: 3 weeks.

Core Web Vitals and SEO — What the Data Shows

Research from Ahrefs and Semrush indicates that:

• Sites with "good" CWV have a 24% higher CTR than sites with "poor" scores
• Improving LCP by 0.1s = 1% increase in conversions (per Google)
• 53% of mobile users abandon a page that takes > 3 seconds to load

Summary: Prioritising Fixes

If you don't know where to start:

1. LCP first — strongest impact on SEO and conversion
2. Then CLS — frustrates users, relatively easy to fix
3. Finally INP — requires code analysis, but improves UX

Optimising Core Web Vitals is an investment with a direct impact on Google visibility and conversion. At Soft Synergy every site we deliver starts with a 90+ PageSpeed score — that's our standard, not an option.