Page speed and Core Web Vitals: the essentials for business owners
LCP, INP, CLS: what Google's Core Web Vitals measure, why your website's speed matters, how to test it for free and what to fix first, explained without jargon.
A slow website costs you customers. Visitors lose patience, especially on mobile, and Google takes page experience into account in its rankings. To measure that experience, Google uses three metrics called Core Web Vitals. You don’t need to be a developer to understand them: here are the essentials, without unnecessary jargon.
The three metrics
LCP: how fast the main content appears
Largest Contentful Paint measures how long it takes to display the largest visible element on load, often a large image or the main headline. Google considers it good below 2.5 seconds.
INP: how responsive the page is
Interaction to Next Paint measures the delay between a visitor’s action (click, tap, key press) and the page’s visible response. It is good below 200 milliseconds. A high INP makes a site feel sluggish.
CLS: how stable the layout is
Cumulative Layout Shift measures unexpected movement: a button that moves just as you click, text that jumps when an image loads. It is good below 0.1.
How to test your website for free
- PageSpeed Insights: enter a page address to get the metrics (real-user data when available) and a list of recommendations.
- Google Search Console: the “Core Web Vitals” report groups pages by status (good, needs improvement, poor).
Test the mobile version first, and not just your home page: product, service and contact pages matter just as much.
The most common causes and their fixes
Oversized images
This is the number one cause. A multi-megabyte photo at the top of the page is enough to hurt LCP.
- resize images to their real display size;
- use modern formats (WebP, AVIF);
- lazy-load images further down the page.
Too many scripts
Chat widgets, pop-ups, embeds, ad pixels, plug-ins: every script weighs on the page and can hurt INP. Take stock and remove what you no longer use. Analytics tools should load after cookie consent, which is also good for performance.
Elements without dimensions
Images, videos, banners or cookie bars appearing without reserved space cause layout shifts (CLS). Always reserve their space.
Poorly loaded fonts
Too many web fonts, or badly configured ones, delay text display. Limit the number of fonts and weights, and host them on your own site if possible.
Heavy hosting or themes
Some themes and page builders load a lot of unnecessary code. Sometimes, changing hosting or theme is the most effective fix.
Where to start?
- Test your five most visited pages on mobile.
- Fix oversized images.
- Remove unnecessary scripts.
- Reserve space for elements that load late.
- Re-test, then check Search Console every month.
Speed that serves conversion
A faster site doesn’t only help SEO: it reduces drop-offs and increases conversions. It is one of the 12 levers to improve your conversion rate.
Frequently asked questions
Does a good PageSpeed score guarantee better rankings? No. Speed is one criterion among many; relevance and content quality remain essential. But a slow site starts with a handicap.
Why do my results change from one test to the next? Lab tests vary with conditions. Rely mainly on real-user data, shown in PageSpeed Insights and Search Console.
We can audit your website
Technical performance is part of every audit in our website optimisation service. Your first audit is free.
