How to Fix Slow Pages and Core Web Vitals
Core Web Vitals measure how fast a page feels: how quickly the main content appears, how quickly it responds and how stable it stays. Each one has a short list of common causes.
The three numbers to aim for
| Metric | Measures | Good |
|---|---|---|
| LCP | When the main content appears | 2.5 s or less |
| INP | How quickly the page responds to input | 200 ms or less |
| CLS | How much the layout shifts | 0.1 or less |
Run the Page Speed Test to see your numbers. Scores vary between runs, and a brand-new deployment can look slower until caches fill, so test more than once.
Lab tests simulate a visit. Field data comes from real Chrome users, and that’s what Google uses for page experience. A new site may have no field data yet.
Fix a slow LCP
The largest element is usually a hero image or headline. Start with the image:
- Compress it and resize it to the size it’s shown at, and use WebP or AVIF.
- Never lazy-load the main image, and tell the browser it matters:
<img src="hero.webp" width="1200" height="630" fetchpriority="high" alt="...">- Check the server is responding quickly. Slow hosting holds back everything after it, so use a CDN and cache your HTML where you can.
- Turn on compression, and confirm it with the Website Compression Test.
Fix a slow INP
INP is poor when JavaScript keeps the browser busy, so taps and clicks wait. Third-party scripts such as chat widgets and trackers are frequent causes.
- Remove scripts you don’t need, and load the rest with
defer. - Delay heavy work until after the page has loaded, or until someone needs it.
- Break long tasks into smaller pieces, so the browser can respond between them.
Fix a high CLS
Content jumps when something loads late and pushes everything down.
- Give every image and video a
widthandheight. - Reserve space for ads and embeds with a fixed minimum height.
- Avoid adding banners above content that has already loaded.
Where to start
Fix your most visited templates first. A home page, a product page and a blog post template usually cover most of a site. Change one thing at a time and test again, so you know what helped.
