Core Web Vitals Explained: A Marketer's Guide to LCP, CLS, and INP

Core Web Vitals are Google's metrics for measuring user experience. They affect both your SEO rankings and conversion rates. Here's everything you need to know, explained without the technical jargon.

What Are Core Web Vitals?

Core Web Vitals are three specific metrics that measure:

1. Loading performance (LCP)

2. Visual stability (CLS)

3. Interactivity (INP)

Google uses these to determine if your page provides a good user experience.

Why Should Marketers Care?

Core Web Vitals impact:

• **SEO Rankings:** Google uses them as a ranking factor
• **Conversions:** Faster pages convert better (1s delay = 7% fewer conversions)
• **Bounce Rate:** 53% of mobile users leave if page takes >3 seconds
• **Ad Quality Score:** Better scores = lower ad costs

LCP: Largest Contentful Paint

What it measures: How long until the main content is visible

Good score: Under 2.5 seconds

Needs improvement: 2.5-4 seconds

Poor: Over 4 seconds

What Affects LCP?

• Hero image size and format
• Server response time
• Render-blocking JavaScript/CSS
• Slow third-party scripts

How to Improve LCP

1. Optimize images

- Use WebP format (30% smaller than JPEG)

- Compress images to under 200KB

- Use lazy loading for below-fold images

2. Improve server response

- Use a CDN

- Enable caching

- Upgrade hosting if needed

3. Remove render-blocking resources

- Defer non-critical JavaScript

- Inline critical CSS

CLS: Cumulative Layout Shift

What it measures: How much the page content moves around while loading

Good score: Under 0.1

Needs improvement: 0.1-0.25

Poor: Over 0.25

What Causes CLS?

• Images without dimensions
• Ads that load late
• Fonts that swap after loading
• Dynamic content insertion

How to Improve CLS

1. Always set image dimensions

```html

<img src="hero.jpg" width="800" height="400" alt="Hero image">

```

2. Reserve space for ads

- Use placeholder divs with fixed heights

3. Preload fonts

- Use font-display: swap

- Preload critical fonts

4. Avoid inserting content above existing content

INP: Interaction to Next Paint

What it measures: How quickly the page responds to user interactions (clicks, taps, key presses)

Good score: Under 200ms

Needs improvement: 200-500ms

Poor: Over 500ms

*Note: INP replaced FID (First Input Delay) in March 2024*

What Causes Poor INP?

• Heavy JavaScript execution
• Long tasks blocking the main thread
• Too many event listeners
• Complex DOM updates

How to Improve INP

1. Break up long JavaScript tasks

2. Reduce JavaScript bundle size

3. Use web workers for heavy computations

4. Debounce rapid interactions

How to Check Your Core Web Vitals

Free Tools

1. Google PageSpeed Insights

- URL: pagespeed.web.dev

- Shows both lab and field data

2. Google Search Console

- Core Web Vitals report

- Shows site-wide issues

3. Chrome DevTools

- Lighthouse tab

- Performance tab for detailed analysis

4. FixRoast

- Analyzes Core Web Vitals

- Provides actionable recommendations

- Shows impact on conversions

Core Web Vitals Benchmarks by Industry

Quick Wins Checklist

• [ ] Compress all images to WebP format
• [ ] Add width/height to all images
• [ ] Preload hero image
• [ ] Enable browser caching
• [ ] Use a CDN
• [ ] Minimize third-party scripts
• [ ] Preload critical fonts
• [ ] Defer non-critical JavaScript

The Connection to Conversions

Core Web Vitals aren't just about SEO. Real data shows:

• **Vodafone:** 31% improvement in LCP → 8% increase in sales
• **NDTV:** 55% reduction in bounce rate after CWV optimization
• **Tokopedia:** 55% improvement in LCP → 23% better session duration

Get Your Core Web Vitals Score

FixRoast analyzes your landing page's Core Web Vitals and shows you exactly what to fix, with specific recommendations tailored to your page.

Check Your Vitals Now →