Website speed for business owners: Core Web Vitals in plain English

Why speed matters

A slow website costs you twice. People leave before the page loads, and Google uses page experience as one of the signals behind its rankings. Most visitors are on their phone, often on a patchy connection, so a site that feels quick on your office Wi-Fi might be frustrating out in the real world. That’s especially true for customers in regional areas, where mobile coverage can be far less forgiving than in the city.

Google measures this with a set of metrics called Core Web Vitals. They sound technical, but each one maps to something a visitor genuinely feels.

The three metrics

• Largest Contentful Paint (LCP) measures how long the main content, usually the hero image or headline, takes to appear. Aim for 2.5 seconds or less.
• Interaction to Next Paint (INP) measures how quickly the page responds when someone taps or clicks. Aim for 200 milliseconds or less.
• Cumulative Layout Shift (CLS) measures how much the page jumps around while loading. Aim for 0.1 or less. You know the feeling: you go to tap a button and something loads above it, pushing it down.

How to check your site

Go to Google's PageSpeed Insights and enter your website address. If your site gets enough traffic, you'll see real-world data from Chrome users at the top. Below that is a lab test with specific recommendations. Check your key pages on mobile, not just the homepage.

Google Search Console also has a Core Web Vitals report that groups your pages by status, which is handy for spotting problems across a whole site.

Reading the results without panicking

The big score out of 100 at the top of PageSpeed Insights is a lab test on a simulated slow phone. It’s useful for finding problems, but it’s not what Google uses for rankings. The real-world data, labelled as what your actual visitors experienced, matters more. A site can score 70 in the lab and still pass Core Web Vitals comfortably for real users.

Focus on the items marked as failing, fix the biggest ones, and don’t chase a perfect 100 at the expense of a site that looks and works well.

The usual culprits

• Huge images. A photo straight off a camera can be several megabytes. Resize images to the size they're displayed and use modern formats like WebP or AVIF.
• Too many scripts. Chat widgets, tracking pixels, booking embeds and pop-ups all add weight.
• Heavy fonts. Loading lots of weights and styles slows things down.
• Bloated themes and plugins, especially on WordPress.
• Images and embeds without set dimensions, which shift the layout as they load.
• Cheap or overloaded hosting, or servers on the other side of the world from your customers.

Quick wins

• Compress and resize every image on your key pages
• Lazy load images further down the page, but not the hero image
• Remove unused plugins, apps and tracking scripts
• Delay non-essential scripts like chat widgets until after the page loads
• Give images and video embeds fixed dimensions

Our website optimisation checklist puts these alongside the other improvements worth making.

Platform by platform

• Squarespace handles hosting and much of the technical setup for you. Most speed problems come from oversized images and too many embedded blocks. See our Squarespace service.
• WordPress can be very fast or very slow depending on the theme, plugins and hosting. It rewards careful setup. See our WordPress service.
• Framer sites are built on modern infrastructure and are usually quick out of the box, as long as animations and video are used sensibly. See our Framer service.
• Custom-coded sites give you full control over performance. See our custom website service.

When it's the platform

Sometimes the problem is baked into how a site was built. If you've done the quick wins and your scores are still poor, a rebuild on a faster foundation can be the better investment. If you’re weighing that up, our guides to choosing a platform and switching platforms without losing rankings are good next reads.

Speed isn't everything

A fast site with confusing content still won't convert. Treat speed as the foundation. It gets people through the door, then your design and copy do the rest.