How to Improve Core Web Vitals: LCP, FID, CLS Explained

What Are Core Web Vitals?

Core Web Vitals are Google's metrics for measuring real user experience. They directly impact your search rankings since 2021. There are three main metrics:

- **LCP (Largest Contentful Paint)** — How fast the main content loads. Target: under 2.5 seconds.

- **FID/INP (First Input Delay / Interaction to Next Paint)** — How fast the page responds to user interaction. Target: under 200ms.

- **CLS (Cumulative Layout Shift)** — How much the page layout shifts during loading. Target: under 0.1.

How to Fix LCP

LCP is usually caused by large images, slow server response, or render-blocking resources.

1. **Optimize your hero image** — Use WebP format, set explicit width/height, add fetchpriority="high"

2. **Reduce server response time** — Use a CDN (Cloudflare is free), enable compression (gzip/brotli)

3. **Remove render-blocking CSS** — Inline critical CSS, defer non-critical stylesheets

4. **Preload key resources** — Add `<link rel="preload">` for your largest image and main font

How to Fix CLS

CLS happens when elements shift position after the page starts rendering.

1. **Set dimensions on images and videos** — Always include width and height attributes

2. **Reserve space for ads and embeds** — Use CSS aspect-ratio or min-height

3. **Avoid inserting content above existing content** — Don't push content down with late-loading banners

4. **Use font-display: swap** — Prevents invisible text while fonts load

How to Fix INP

INP measures responsiveness to all user interactions, not just the first one.

1. **Break up long tasks** — Use `requestIdleCallback` or `setTimeout` to split heavy JavaScript

2. **Reduce JavaScript bundle size** — Code-split with dynamic imports

3. **Avoid long main thread blocking** — Move heavy computation to Web Workers

4. **Minimize third-party scripts** — Each analytics/chat/ad script adds latency

Measure Your Vitals

Use [SEO Snapshot](/) to check your Core Web Vitals. We integrate with Google PageSpeed Insights API to show real lab data, and Chrome UX Report (CrUX) for real user field data.