Core Web Vitals – what they are and how to use them

Your content is in place, links are working, but customers are finding you less and less on Google? Most likely, the reason lies in algorithm updates and the new focus of search engines on user experience.

Google has long shifted from simple keyword analysis to a comprehensive evaluation of websites. Now, it’s not just about texts and links but also about loading speed, interface responsiveness, and layout stability. These parameters are combined into a single metric — Core Web Vitals (CWV).

Even the best content won’t save the situation if users find the site inconvenient to use.

In this article

• I will explain how Core Web Vitals impact Google rankings.
• I will show you how to check CWV on your site.
• I will provide a step-by-step improvement plan to boost your traffic.

What are Core Web Vitals and what metrics do they include?

Previously, SEO was all about working with keywords, links, and technical optimization. Now, factors such as loading speed, interface responsiveness, and visual stability of the page play a crucial role.

Why are Core Web Vitals important?

• Google uses them as a ranking factor — websites with poor CWV lose positions.
• They directly affect user behavior: the faster and more stable the site, the higher the conversions and time spent on the page.
• Good CWV scores improve the mobile experience, which is critical since more than 60% of traffic in 2024 comes from mobile devices.

Google highlights three key metrics that evaluate loading speed, interactivity, and page stability:

Largest Contentful Paint (LCP) – loading speed of the main content

LCP measures the time it takes to display the largest element on a page (such as an image, heading, or video). The faster the main content loads, the better.

Optimal values:

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

What affects LCP?

• Image size and format.
• Server response time.
• Inefficient use of CSS and JavaScript.

How to improve it?

• Use Lazy Load for images.
• Move heavy scripts to the end of the page.
• Set up caching and a CDN.

First Input Delay (FID) → Interaction to Next Paint (INP)

FID measures the delay between a user’s first interaction with a site (such as clicking a button) and the moment when the browser responds.

As of January 2024, Google replaced FID with Interaction to Next Paint (INP), which evaluates not just the first interaction but the overall responsiveness of a website.

INP thresholds:

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

What affects INP?

• Heavy and poorly optimized JavaScript scripts.
• The number of background tasks running in the browser.
• The complexity of the DOM structure.

How to improve it?

• Remove unnecessary JavaScript libraries.
• Use defer and async for script loading.
• Minimize CSS and HTML code.

Cumulative Layout Shift (CLS) – visual stability

CLS measures how much elements shift on a page during loading.

Example: You want to click the “Buy” button, but at the last moment, it shifts due to a loading banner — this indicates a high CLS.

Optimal values:

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

What affects CLS?

• Dynamically loaded ads.
• Images and videos without fixed dimensions.
• Slow font loading.

How to improve it?

• Set fixed dimensions (width/height) for images and banners.
• Use the font-display: swap attribute for fonts.
• Place ad blocks in reserved spaces instead of loading them dynamically.

Impact of Core Web Vitals on SEO

If two websites with equally high-quality content compete in search rankings, Google will prioritize the one that loads faster and offers a better user experience. This has become even more critical after Google’s algorithm updates, where user experience (UX) is now a key ranking factor.

Here are the top three reasons why Core Web Vitals affect SEO:

• Slow site = ranking drop
  If LCP exceeds 4 seconds, the website may lose up to 30% of traffic due to slow loading.
• Poor CLS = lost sales
  When a page layout is unstable, the bounce rate increases by 20-25%, especially in e-commerce.
• Fast site = advantage in mobile search
  More than 60% of users browse from mobile devices, and if a website takes longer than 3 seconds to load, 53% of users leave it.

Case Studies of Core Web Vitals Optimization

The BUSINESS SITE team has already helped dozens of clients improve their Core Web Vitals and achieve higher rankings. Here are real case studies from our clients.

Case 1: Optimizing an Electronics Online Store

💡 Problem: Slow loading speed (LCP = 5.2 sec), causing customers to leave before product pages loaded.

🚀 What we did:

• Migrated the website to a CDN to speed up content delivery.
• Optimized images by converting them to WebP format.
• Enabled Lazy Load to load content progressively as users scroll.

📊 Results:

• ✅ LCP improved to 1.9 sec.
• ✅ Conversion rate increased by 17%.
• ✅ Average Google ranking improved by 5 positions.

Case 2: Improving CWV for a SaaS Service

💡 Problem: Slow request processing and delayed button response (INP = 450 ms).

🚀 What we did:

• Removed unnecessary JavaScript libraries and optimized the code.
• Implemented defer and async for script loading.
• Used Web Workers to handle background tasks efficiently.

📊 Results:

• ✅ INP reduced to 180 ms.
• ✅ 21% more users completed the registration process.
• ✅ Average session duration increased by 12%.

Case 3: Optimizing CLS for a Large News Portal

💡 Problem: Ad placements were causing content “jumps” during page loading (CLS = 0.35), increasing bounce rates.

🚀 What we did:

• Set fixed dimensions for images and banners in the code.
• Disabled dynamic ad loading without reserved space.
• Implemented the font-display: swap attribute for fonts.

📊 Results:

• ✅ CLS decreased to 0.07.
• ✅ Bounce rate dropped by 14%.
• ✅ Time spent on the page increased by 9%.

Tools for Analysis and Optimization

The first step is diagnosing issues. To identify which metrics need improvement and get optimization recommendations, you can use specialized tools.

Here are the key tools to measure and improve CWV:

• Google PageSpeed Insights – analyzes loading speed and provides improvement recommendations.
• Lighthouse – a built-in tool in Chrome DevTools that audits website performance.
• WebPageTest – allows testing page load speeds in different regions and on different devices.
• Cloudflare APO – accelerates WordPress sites through caching and request optimization.
• NitroPack – automates website optimization, including code modifications and speed improvements.

Each of these tools helps not only measure Core Web Vitals but also find ways to improve them. In the following sections, we will explore the steps that can help achieve the best results.

Conclusion

Core Web Vitals are not just technical parameters but a crucial factor influencing SEO, user experience, and conversions. If a website loads slowly, responds with delays, or behaves unstably, Google lowers its ranking, and users leave for competitors.

Key takeaways:

• Core Web Vitals directly impact search rankings—fast and user-friendly websites get priority.
• Poor CWV scores lead to lost customers—a slow or unstable website reduces conversions and increases bounce rates.
• Optimizing CWV brings real results—case studies show that improving LCP, INP, and CLS leads to better rankings, more traffic, and higher sales.
• There are accessible tools for checking and improving CWV—you can use them to diagnose issues and work on fixing them.

What to do next?

1. Check your website using Google PageSpeed Insights or Lighthouse.
2. Identify weak points and determine which CWV metrics need improvement.
3. Optimize your website by fixing LCP, INP, and CLS issues with caching, image optimization, and code refinement.
4. Continuously monitor performance, as search engine requirements change, and it’s important to keep your site in top shape.

If you don’t have the time or expertise to work on Core Web Vitals, the BUSINESS SITE team can help. We will audit your site, fix critical issues, and optimize performance to make it faster, more user-friendly, and rank higher in search results.