Core Web Vitals: What They Are & How to Improve Them

Google recommends every business owner be familiar with these vitals as they play a key role in optimizing the user engagement rate and ranking of your website. While the name “core web vitals” might sound technical and complex, business owners need not be performance experts to understand this and use it to their success. This blog is the ultimate guide for all business owners, it covers everything about core web vitals, how to implement them, how to monitor them, and most importantly how to optimize them for better results.

What are core web vitals?

Core web vitals are quality signals(a set of metrics) that Google considers essential for great user experience on the web. These are used to measure the real-world user experience. Every website is analyzed by these quality metrics for speed, interactivity, and visual aesthetics of the page. Google then analyzes these metrics and ranks them based on the same metrics.

The user engagement rate directly correlates with the user experience, speed, and interactivity on the page. The better the user experience, the better the engagement rate. They focus on three key aspects:

1. Largest Contentful Paint (LCP) – Measures loading performance
2. First Input Delay (FID) / Interaction to Next Paint (INP) – Measures interactivity
3. Cumulative Layout Shift (CLS) – Measures visual stability

All of these metrics are part of Google’s Page Experience Signals which directly influences your website’s rankings and engagement.

1. Largest Contentful Paint (LCP) – How Fast Your Page Loads

LCP measures the time it takes for the largest visible element (like an image or heading) to fully load.

• Good LCP Score: Under 2.5 seconds
• Poor LCP Score: More than 4 seconds

How to Improve LCP?

• Optimize and compress images (WebP format is best).
• Enable lazy loading to ensure images load only when they are needed.
• Improve server response time (reduce TTFB – Time to First Byte).
• Utilize a Content Delivery Network (CDN) to speed up load times.
• Minimize JavaScript and CSS blocking critical rendering.

2. First Input Delay (FID) / Interaction to Next Paint (INP) – How Quickly Your Site Responds

• FID (Old Metric – Until March 2024): Measures the time it takes for a page to respond to the first user interaction (like clicking a button).
• INP (New Metric – Replacing FID in March 2024): Measures the overall responsiveness of a page, considering multiple interactions, not just the first one.
• Good INP Score: Under 200ms
• Poor INP Score: More than 500ms

How to Improve INP?

• Optimize JavaScript execution (reduce unused JS).
• Use web workers to handle background tasks efficiently.
• Minimize long-running tasks blocking the main thread.
• Reduce third-party scripts that slow down interaction.

3. Cumulative Layout Shift (CLS) – How Stable Your Page Layout Is

Measures how many elements unexpectedly move while the page loads. This is important for visual stability.

• Good CLS Score: Less than 0.1
• Poor CLS Score: More than 0.25

How to Improve CLS?

• Always define image and video dimensions in CSS.
• Use font-display: swap to avoid Flash of Invisible Text (FOIT).
• Avoid inserting ads or dynamic content above existing content.
• Use CSS animations instead of layout shifts.

How to measure core web vitals?

Core web vitals are measured majorly using two types of data, field data and lab data.

Field Data (Real-User Data - RUM)

• Collected from LIVE real-world users visiting your site.
• Helps identify performance issues based on multiple actual user conditions (device, network, location).
• Used by Google’s CrUX (Chrome User Experience Report).
• Found in Google Search Console and PageSpeed Insights.

Lab Data (Simulated Data - Synthetic Testing)

• Collected using tools that simulate user visits in controlled conditions.
• Useful for debugging and optimizing before deploying changes.
• Found in Lighthouse, Chrome DevTools, and GTmetrix.

Best tools to measure core web vitals

Google’s Tools (Recommended for accuracy & real-user data)

1. PageSpeed Insights (PSI) – Quick Performance Report

What It Does:

• Provides both Field Data (real user experience) and Lab Data (simulated test).
• Shows a Core Web Vitals assessment (Pass/Fail).
• Gives recommendations for performance improvements.

How to Use It?

• Go to PageSpeed Insights.
• Enter your website URL and click Analyze.
• Check LCP, INP (or FID), and CLS scores.
• Follow the optimization suggestions.

2. Google Search Console (GSC) – Long-Term Performance Tracking

What It Does:

• Provides real-user data from Google’s Chrome User Experience Report (CrUX).
• Shows trends and Core Web Vitals reports for all indexed pages.
• Helps detect which pages Fail or need Improvement.

How to Use It?

• Go to Google Search Console.
• Click on Core Web Vitals in the left panel.
• Analyze Mobile vs. Desktop performance separately.
• Identify pages marked as Poor or Needs Improvement and fix them.

3. Lighthouse (Chrome DevTools) – In-Depth Debugging

What It Does:

• Provides detailed diagnostics on Core Web Vitals.
• Analyzes website performance, accessibility, SEO, and best practices.
• Simulates different network and device conditions.

How to Use It?

• Open Google Chrome.
• Press Ctrl + Shift + I (Windows) or Cmd + Option + I (Mac) to open DevTools.
• Click on the Lighthouse tab.
• Select Performance and run an analysis.

4. Chrome User Experience Report (CrUX) – Real-World Data Analysis

What It Does:

• Provides historical Core Web Vitals data based on actual Chrome users.
• Aggregated data is available via BigQuery and PageSpeed Insights.

How to Use It?

• Check Field Data in PageSpeed Insights (powered by CrUX).
• Use Google Data Studio to visualize CrUX data.
• Click on the Lighthouse tab.
• Select Performance and run an analysis.

Third-Party Performance Tools

1. GTmetrix – Performance & Web Vitals Insights

What It Does:

• Tests Core Web Vitals from different locations, devices, and network speeds.
• Gives Waterfall Analysis (shows what loads first and what slows the page).

How to Use It?

• Visit GTmetrix.
• Enter your website URL and start a test.
• Check LCP, INP, CLS, and performance recommendations.

2. WebPageTest – Advanced Performance Testing

What It Does:

• Simulates real-user conditions (different browsers, devices, locations).
• Provides a detailed Waterfall of loading elements.

How to Use It?

• Go to WebPageTest.
• Enter your URL and choose test conditions.
• Check Web Vitals scores and recommendations.

3. Cloudflare Web Analytics – Core Web Vitals for CDN Users

What It Does

• Provides real-user monitoring if you use Cloudflare’s CDN.
• Measures Core Web Vitals without JavaScript tracking.

How to Use It?

• Enable Cloudflare Web Analytics in your account dashboard.
• Best for: Websites using Cloudflare to analyze performance.

Here is the detailed breakdown of all the tools, their capabilities, and what they are best used for.

Common core web vitals mistakes and how to fix them?

Simple steps

Mistake 1: Not Optimizing Images

Fix: Compress images, use WebP, and enable lazy loading.

Mistake 2: Too Many JavaScript & Third-Party Scripts

Fix: Reduce scripts, and load essential ones asynchronously.

Mistake 3: Slow Hosting & Poor Server Response

Fix: Use a fast web host, enable caching, and use a CDN.

Mistake 4: Unexpected Layout Shifts

Fix: Set height/width attributes for images, preload fonts, and avoid inserting ads dynamically.

Conclusion

All in all, understanding the web vitals is important for every website owner. It is essential for analyzing your website’s performance and gives you various recommendations to boost user engagement. However, if you are a professional who has a very busy schedule to make room for this, partner with a reliable web development and digital marketing agency. Webomindapps is a leading web development company in Dubai, we offer a range of development and maintenance services including optimizing the core web vitals. Partner with us to make sure your website is optimized and ranks on the top pages of search results.