Core Web Vitals Guide: Boost Your SEO and CTR in 2023

Learn how to check, optimize, and improve your Core Web Vitals for better search rankings and higher click-through rates (CTR). Complete step-by-step guide.

Table of Contents

Core Web Vitals Guide: Boost Your SEO and CTR in 5 Steps

Last Updated: September 15, 2023 6 min read

Core Web Vitals are essential metrics that measure user experience on your website and directly impact your search rankings and click-through rates. In this guide, we'll show you exactly how to measure, understand, and improve your Core Web Vitals to boost both your SEO performance and CTR.

1. What Are Core Web Vitals?

Core Web Vitals are a set of specific factors that Google considers important for user experience on a webpage. These metrics have become an official ranking factor, directly affecting your search visibility and click-through rates.

Largest Contentful Paint (LCP)

Measures: Loading performance

Good score: ≤ 2.5 seconds

LCP measures how quickly the main content of your page becomes visible to users. Faster LCP creates the perception of a speedy site.

First Input Delay (FID)

Measures: Interactivity

Good score: ≤ 100 milliseconds

FID measures the time from when a user first interacts with your page to when the browser can begin processing that interaction.

Cumulative Layout Shift (CLS)

Measures: Visual stability

Good score: ≤ 0.1

CLS measures how much visible content shifts around during page loading. Lower scores mean less unexpected movement.

How Core Web Vitals Impact CTR

Google found that as page load time increases from 1s to 3s, the probability of bounce increases by 32%. Sites that meet Core Web Vitals standards see:

  • 24% fewer abandons
  • Up to 35% lower bounce rates
  • Significant increases in organic CTR
  • Higher conversion rates (by up to 27%)

2. How to Measure Your Core Web Vitals

Before you can improve your scores, you need to know where you stand. Here are the best tools to measure your Core Web Vitals:

PageSpeed Insights

PageSpeed Insights screenshot

Provides both lab and field data for all Core Web Vitals metrics. Simply enter your URL and get a comprehensive report.

Open Tool

Chrome DevTools

Chrome DevTools screenshot

Use the Performance and Network panels to analyze load times, JavaScript execution, and layout shifts.

Tip: Press F12 in Chrome to open DevTools

Search Console

Search Console screenshot

View Core Web Vitals data for your entire site and identify pages that need improvement.

Open Tool

Quick Measurement with JavaScript

You can also measure Core Web Vitals directly in your browser console:

// Check LCP
new PerformanceObserver((entryList) => {
  const entries = entryList.getEntries();
  const lastEntry = entries[entries.length - 1];
  console.log('LCP:', lastEntry.startTime / 1000, 'seconds');
}).observe({type: 'largest-contentful-paint', buffered: true});

// Check CLS
let cls = 0;
new PerformanceObserver((entryList) => {
  for (const entry of entryList.getEntries()) {
    if (!entry.hadRecentInput) {
      cls += entry.value;
    }
  }
  console.log('CLS:', cls);
}).observe({type: 'layout-shift', buffered: true});

3. Optimizing Largest Contentful Paint (LCP)

LCP measures how quickly the largest content element (image, video, or text block) becomes visible to users. Here's how to improve it:

Eliminate Render-Blocking Resources

Render-blocking resources prevent your page from displaying quickly. To fix:

  • Move critical CSS inline
  • Defer non-critical CSS with media="print" or rel="preload"
  • Use async or defer attributes on non-critical scripts
  • Consider code-splitting your JavaScript bundles
<!-- Before -->
<link rel="stylesheet" href="styles.css">
<script src="app.js"></script>

<!-- After -->
<style>
  /* Critical CSS here */
</style>
<link rel="stylesheet" href="styles.css" media="print" onload="this.media='all'">
<script src="app.js" defer></script>

Optimize Images

Images are often the largest content elements and key to LCP optimization:

  • Use modern formats like WebP or AVIF
  • Implement responsive images with srcset
  • Compress images without sacrificing quality
  • Consider a CDN for image hosting
  • Preload important images
<!-- Preload critical hero image -->
<link rel="preload" as="image" href="hero.webp">

<!-- Responsive images -->
<img 
  srcset="hero-small.webp 400w, hero-medium.webp 800w, hero-large.webp 1200w"
  sizes="(max-width: 600px) 400px, (max-width: 1200px) 800px, 1200px"
  src="hero-medium.webp"
  alt="Hero image"
  width="800"
  height="450"
>

Optimize Server Response Time

A slow server delays everything else. Here's how to improve:

  • Use a performance-optimized hosting provider
  • Implement server-side caching
  • Consider a CDN for static assets
  • Optimize database queries
  • Minimize HTTP requests

4. Improving First Input Delay (FID)

FID measures the time from when a user first interacts with your site to when the browser can respond. Here's how to optimize it:

Minimize JavaScript Execution Time

Heavy JavaScript processing is the primary cause of poor FID. To improve:

  • Break up long-running tasks (> 50ms)
  • Use Web Workers for CPU-intensive tasks
  • Remove unused JavaScript
  • Defer or lazy-load non-critical scripts
// Before: Long-running task blocking the main thread
function processData(items) {
  for (let i = 0; i < items.length; i++) {
    // Heavy processing here
  }
}

// After: Break into smaller chunks with requestIdleCallback
function processData(items) {
  const chunk = 100;
  let index = 0;
  
  function doChunk() {
    const stop = Math.min(index + chunk, items.length);
    for (let i = index; i < stop; i++) {
      // Process item
    }
    index = stop;
    
    if (index < items.length) {
      // More to do, schedule next chunk
      window.requestIdleCallback(doChunk);
    }
  }
  
  window.requestIdleCallback(doChunk);
}

Optimize Third-Party Impact

Third-party scripts often significantly impact FID:

  • Audit and remove unnecessary third-party scripts
  • Load third-party scripts after critical content
  • Use async or defer for third-party scripts
  • Consider self-hosting critical third-party scripts

Implement Browser Hints

Browser hints can prepare resources before they're needed:

  • Use preconnect for important third-party domains
  • Use dns-prefetch for less important domains
  • Consider implementing prefetch for resources needed on next page
<!-- Preconnect to critical third-party domains -->
<link rel="preconnect" href="https://analytics.example.com">
<link rel="dns-prefetch" href="https://fonts.googleapis.com">

<!-- Prefetch for next page resources -->
<link rel="prefetch" href="/next-page.js">

5. Fixing Cumulative Layout Shift (CLS)

CLS measures visual stability by quantifying unexpected layout shifts. Here's how to minimize layout shifts:

Set Size Attributes on Media

Always specify dimensions for images and videos:

  • Add width and height attributes to all <img> elements
  • Use aspect-ratio CSS property for responsive elements
  • Set dimensions for video elements and embeds
<!-- Before: No dimensions specified -->
<img src="product.jpg" alt="Product">

<!-- After: Dimensions specified -->
<img src="product.jpg" alt="Product" width="400" height="300">

<!-- CSS for responsive images that maintain aspect ratio -->
img {
  max-width: 100%;
  height: auto;
  aspect-ratio: attr(width) / attr(height);
}

Reserve Space for Dynamic Content

Content that loads after the initial render often causes shifts:

  • Implement content placeholders or skeletons
  • Pre-allocate space for ads and embeds
  • Use min-height for containers that will be populated dynamically
/* Reserve space for an ad that loads later */
.ad-container {
  min-height: 250px;
  width: 100%;
}

/* Create a loading skeleton effect */
.content-skeleton {
  background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
  background-size: 200% 100%;
  animation: loading 1.5s infinite;
  border-radius: 4px;
  min-height: 120px;
  margin-bottom: 10px;
}

@keyframes loading {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

Manage Web Font Loading

Font loading can cause significant layout shifts:

  • Use font-display: swap to show text while fonts load
  • Preload important fonts
  • Consider using system font stacks
  • Set explicit font fallbacks that closely match the web font
<!-- Preload critical fonts -->
<link rel="preload" href="/fonts/roboto.woff2" as="font" type="font/woff2" crossorigin>

<style>
  /* Use system font stack as fallback */
  body {
    font-family: 'Roboto', -apple-system, BlinkMacSystemFont, 'Segoe UI', 
      Roboto, Oxygen-Sans, Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;
  }
  
  /* Set font-display to swap */
  @font-face {
    font-family: 'Roboto';
    src: url('/fonts/roboto.woff2') format('woff2');
    font-display: swap;
  }
</style>

6. Complete Core Web Vitals Checklist

Largest Contentful Paint (LCP) Checklist

First Input Delay (FID) Checklist

Cumulative Layout Shift (CLS) Checklist

Start Checking Your Core Web Vitals Today

By optimizing your Core Web Vitals, you'll not only improve search rankings but also significantly boost your click-through rates. Better user experience means more engagement, longer sessions, and higher conversion rates.

Check Your Site Now