A slow website loses visitors before they read a word, and page experience is one of the signals Google uses in search. Core Web Vitals are Google’s way of measuring that experience. This checklist explains what they are and how to improve them on a WordPress site.

The three Core Web Vitals

Metric What it measures Good score
Largest Contentful Paint (LCP) How quickly the main content, often a hero image or heading, appears 2.5 seconds or less
Interaction to Next Paint (INP) How quickly the page responds when someone taps, clicks or types 200 milliseconds or less
Cumulative Layout Shift (CLS) How much the layout jumps around while the page loads 0.1 or less

Google assesses these at the 75th percentile of real visits, so most of your visitors need a good experience, not just you on fast office Wi-Fi.

Step 1: measure before you change anything

  • PageSpeed Insights shows real-user data (when your site has enough traffic) plus a lab test with specific suggestions.
  • Google Search Console has a Core Web Vitals report that groups your URLs into good, needs improvement and poor.
  • Chrome DevTools helps a developer find exactly which script or image is causing a problem.

Test your home page, a typical blog post and your most important landing page, on mobile first.

Step 2: fix Largest Contentful Paint

  • Use good hosting with server-side caching. A slow server delays everything that follows.
  • Compress images and serve modern formats such as WebP or AVIF at the size they are displayed.
  • Do not lazy-load the hero image. Load it first, and consider fetchpriority="high" on it.
  • Self-host fonts, limit the number of weights, and preload the one used above the fold.
  • Remove render-blocking CSS and JavaScript that the first screen does not need.

Step 3: fix Interaction to Next Paint

  • Audit your plugins. Every slider, chat widget, popup and tracking script adds JavaScript that competes for the browser’s attention.
  • Delay non-essential third-party scripts until the visitor interacts with the page.
  • Avoid heavy page builders on key pages if you can; they often ship far more code than the page needs.
  • Defer your theme’s own scripts and keep them small.

Step 4: fix Cumulative Layout Shift

  • Set width and height on every image and video so the browser reserves space.
  • Reserve space for ads, embeds and cookie banners instead of letting them push content down.
  • Use font-display: swap with a fallback font of similar size to reduce text jumping.
  • Do not insert content above what the visitor is already reading.

Step 5: keep it fast

Speed is not a one-off job. New plugins, larger images and extra tracking scripts creep in over time. Re-test after every significant change, and check the Search Console report monthly.

When to rebuild instead of patch

If a site relies on a heavy multipurpose theme, a page builder and dozens of plugins, optimisation plugins can only go so far. A lean custom theme often fixes the problem at the root and makes the site easier to manage. We build ours with self-hosted fonts, no jQuery, and only the code each page needs.

Want to know why your site is slow? Ask us for a speed audit and we will show you what to fix first.