Core Web Vitals: a practical guide to making your website load fast (LCP, INP and CLS)

Core Web Vitals are three metrics Google uses to evaluate the user experience of a page. They influence rankings and, above all, whether your visitors leave before seeing anything.

The three metrics

How to measure them

• PageSpeed Insights: gives lab data and real user data (if there is enough traffic).
• Search Console → Core Web Vitals: report by URL groups.
• Chrome DevTools → Lighthouse: local tests and diagnosis.
• Always test on mobile and a normal connection, not on your computer and fibre.

How to improve LCP

• Optimise the main image or block: compress, use modern formats (WebP, AVIF) and suitable sizes.
• Make that element load with priority (fetchpriority="high"), and do not lazy-load it.
• Reduce server response time: page caching, good hosting, a CDN.
• Remove CSS and JavaScript that block rendering.
• Preload the main font or use system fonts.

How to improve INP

• Reduce JavaScript: remove scripts and plugins that add nothing.
• Delay third-party scripts (chat, analytics, pixels) until they are needed.
• Split long main-thread tasks.
• Avoid heavy event handlers on buttons and forms.

How to improve CLS

• Declare width and height on images, videos and iframes.
• Reserve space for banners, ads and blocks that load later.
• Avoid inserting content above what is already visible.
• Mind the effect of fonts loading (use font-display and preload).

Particulars of WooCommerce and WordPress

• Review plugins: each one adds code. Remove those you do not use.
• Use a lightweight theme and a well-optimised builder.
• Enable page and object caching, and be careful to exclude cart and checkout from the cache.
• Optimise product images when uploading them.
• Limit third-party scripts and respect cookie consent.

In-app browsers

Many visitors arrive from ads and open the site inside the Facebook or Instagram app. That browser is usually slower and more limited. Test your site there: if it loads slowly, part of the paid traffic is lost before anything is shown.

How to prioritise

1. Look at which pages have the most traffic and the worst data.
2. Fix first what affects all of them (template, theme, global scripts).
3. Then the key pages: homepage, categories, product, checkout.
4. Measure again after each change.

A fast website converts better, ranks better and spends less on ads. If you want us to measure yours, we will run a diagnosis.