Core Web Vitals in 2025: Optimising for Speed, Stability, and Interactivity

Core Web Vitals have become essential for SEO success in 2025. These metrics help Google measure how users experience a webpage, going beyond keywords and content quality. If your website loads slowly, shifts unexpectedly, or delays when clicked, users leave—and so does your chance to rank.

This article explains:

• What Core Web Vitals are
  
• Why they matter to search engines
  
• How to improve LCP, INP, and CLS
  
• The best tools for measurement
  
• Practical fixes to optimise your site
  

What Are Core Web Vitals in 2025?

Google’s Core Web Vitals are performance-based SEO signals that reflect how well a page loads and behaves for users. As of 2025, they are:

• LCP (Largest Contentful Paint): Measures how fast the main content loads. Target: ≤ 2.5 seconds.
  
• INP (Interaction to Next Paint): Replaced FID in 2024. Measures responsiveness. Target: ≤ 200 milliseconds.
  
• CLS (Cumulative Layout Shift): Measures how visually stable the page is. Target: ≤ 0.1.
  

These are part of Google’s page experience signals and can affect your rankings, particularly for mobile users (Google Developers, 2024).

Why Core Web Vitals Matter for SEO

Core Web Vitals have moved from optional performance metrics to mandatory ranking signals.

According to Ahrefs (2024):

• Pages with good CWV scores get 23% more organic traffic.
  
• They reduce bounce rate by up to 18%.
  
• They increase time-on-page and conversions.
  

Sites that are fast, responsive, and stable offer a better experience, which Google rewards with higher rankings and better visibility (Google Search Central, 2024).

1. How to Improve Largest Contentful Paint (LCP)

LCP focuses on the time it takes to load the largest visible element on a page—usually a hero image or main headline.

🔧 Ways to Optimise LCP:

• Use a fast web hosting service or CDN (e.g., Cloudflare)
  
• Optimise and compress images using tools like TinyPNG
  
• Serve images in WebP or AVIF formats
  
• Preload fonts and above-the-fold content
  
• Minify CSS and eliminate unused JavaScript
  

Example: A large background image on an eCommerce homepage delayed LCP by 4 seconds. After compression and lazy loading, LCP improved to under 2 seconds.

2. How to Improve Interaction to Next Paint (INP)

INP reflects how quickly your site responds to real user actions like clicking buttons, opening menus, or submitting forms. It replaced FID as the preferred responsiveness metric in March 2024 (Google Developers, 2024).

🔧 Ways to Optimise INP:

• Reduce JavaScript execution time by splitting scripts
  
• Remove unnecessary third-party scripts
  
• Use requestIdleCallback() to delay non-critical functions
  
• Consider switching to lightweight frameworks like Svelte or Alpine.js
  

Example: A site running multiple tracking scripts saw an INP of 420 ms. After deferring these scripts, INP dropped to 150 ms.

3. How to Improve Cumulative Layout Shift (CLS)

CLS measures how much your content jumps around while loading. Unexpected shifts frustrate users and cause misclicks.

🔧 Ways to Optimise CLS:

• Reserve space for images, videos, and ads using width and height attributes
  
• Avoid loading content above the fold dynamically
  
• Use font-display: swap to prevent invisible text
  
• Avoid animations that move elements unexpectedly
  

Example: An ad block loaded late and pushed content down, causing a CLS of 0.3. After defining a fixed height, CLS dropped to 0.05.

4. Best Tools to Measure Core Web Vitals

Tool	Use Case
Google PageSpeed Insights	Quick overview of LCP, INP, CLS
WebPageTest	Deep analysis of load times and resource waterfalls
Lighthouse	Full site audit inside Chrome DevTools
Search Console Core Web Vitals	Tracks page performance trends over time
CrUX Dashboard	Real-world performance data from Chrome users

These tools combine lab data (synthetic) and field data (real-world) for complete visibility.

5. Real-World Case Study: Small Fixes, Big Results

A Cambodian travel agency with poor Core Web Vitals saw:

• LCP: 5.2s
  
• INP: 310ms
  
• CLS: 0.21
  

After implementing:

• Cloudflare CDN
  
• Image compression with WebP
  
• Layout fixes for shifting buttons
  

They achieved:

• LCP: 1.8s
  
• INP: 120ms
  
• CLS: 0.04
  

Their organic search clicks increased by 39% in 2 months.

6. Core Web Vitals and Mobile SEO

Google uses mobile-first indexing, meaning your mobile performance is now the default for rankings (Google Search Central, 2024).

Tips for Mobile Performance:

• Use responsive images via srcset
  
• Avoid intrusive interstitials or popups
  
• Keep file sizes small for 4G or 3G networks
  
• Test using Lighthouse Mobile Emulator
  

7. Mistakes to Avoid

Mistake	Impact
Lazy loading all images	Hurts LCP
Excessive JavaScript	Slows interactivity (INP)
No image dimensions	Causes layout shifts
Optimising only desktop	Misses mobile SEO impact
Relying on lab tools only	Misses real user experience data

8. Summary Table: Key Fixes and Their Benefits

Fix	Metric Improved	Tool to Use
Image Compression	LCP	PageSpeed Insights
Script Deferral	INP	Lighthouse
Fixed Layouts	CLS	WebPageTest
Mobile Testing	All	Chrome DevTools
CDN Usage	LCP	WebPageTest

References

Ahrefs. (2024). Core Web Vitals: The SEO performance metrics that matter most. Retrieved from https://ahrefs.com/blog/core-web-vitals
Google Developers. (2024, March 12). INP replaces FID as a Core Web Vital. Retrieved from https://web.dev/blog/inp-core-web-vital
Google Search Central. (2024). Page experience and Core Web Vitals. Retrieved from https://developers.google.com/search/docs/appearance/page-experience
Moz. (2024). What are Core Web Vitals? Retrieved from https://moz.com/learn/seo/core-web-vitals
WebPageTest. (2024). Real-world speed tests for your site. Retrieved from https://www.webpagetest.org/