# Core Web Vitals: The Technical SEO Guide to Page Experience

Core Web Vitals (CWV) are a set of specific metrics that Google considers important for user experience. They're a confirmed ranking factor, and optimizing them can boost your search visibility.

## The Three Core Web Vitals

### Largest Contentful Paint (LCP)

**What it measures**: How quickly the largest content element loads  
**Target**: Under 2.5 seconds  
**Common issues**:

- Slow server response times
- Render-blocking JavaScript and CSS
- Slow resource loading (fonts, images)
- Client-side rendering delays

**How to fix**:

- Optimize server response time (use a CDN)
- Preload critical resources
- Compress and serve images in next-gen formats (WebP, AVIF)
- Remove render-blocking resources

### Interaction to Next Paint (INP)

**What it measures**: Overall responsiveness to user interactions  
**Target**: Under 200 milliseconds  
**Common issues**:

- Long JavaScript tasks blocking the main thread
- Heavy event handlers
- Excessive DOM size
- Third-party scripts

**How to fix**:

- Break up long tasks using `requestIdleCallback`
- Defer non-critical JavaScript
- Optimize event handlers
- Reduce third-party script impact

### Cumulative Layout Shift (CLS)

**What it measures**: Visual stability — how much content shifts unexpectedly  
**Target**: Under 0.1  
**Common issues**:

- Images without width/height attributes
- Ads or embeds without reserved space
- Dynamically injected content
- Web fonts causing FOIT/FOUT

**How to fix**:

- Always specify image dimensions
- Reserve space for ads and dynamic content
- Use font-display: optional or swap
- Avoid inserting content above existing content

## How to Measure Core Web Vitals

### Lab Data (Development)

- **Chrome DevTools** — Performance panel
- **Lighthouse** — Built into Chrome
- **PageSpeed Insights** — Google's free tool

### Field Data (Real Users)

- **Chrome UX Report** — Real user data
- **Search Console** — Core Web Vitals report
- **web-vitals** library — Measure in production

## The Impact on Rankings

Google uses CWV as a tiebreaker between pages with similar content quality. If you and a competitor have equally good content, better CWV can give you the edge.

## Rankium Integration

Rankium's site audit includes page speed and performance analysis. Our AI identifies specific CWV issues and provides prioritized fixes based on their impact on your rankings.