Core Web Vitals explained for business owners

If you’ve looked at Google Search Console or a website audit, you’ve probably seen “Core Web Vitals” marked in red or green. They’re Google’s way of measuring whether a page feels fast and stable to real visitors. They affect your search rankings, but more importantly, they affect whether people stay on your site long enough to get in touch.

Here’s what they mean in plain English.

The three measurements

Google measures these using data from real visitors’ browsers, and judges your site on how the slower visitors experience it (the 75th percentile), not the fastest ones.

Largest Contentful Paint (LCP): does it load quickly?

How long it takes for the main content (usually the biggest image or headline) to appear. Good is 2.5 seconds or less.

A slow LCP feels like staring at a blank or half-built page.

Interaction to Next Paint (INP): does it respond quickly?

How long the page takes to react when someone taps a button, opens a menu or types in a form. Good is 200 milliseconds or less.

A poor INP feels like a page that ignores you, then suddenly catches up.

Cumulative Layout Shift (CLS): does it stay still?

How much the page jumps around while it loads, for example when an image or advert suddenly pushes the text down. Good is 0.1 or less.

A poor CLS is the reason you tap the wrong link because the page moved at the last moment.

Why it matters for your business

• Rankings: Google uses Core Web Vitals as one of its signals. It won’t outrank great content on its own, but between two similar pages, the faster one has an edge.
• Conversions: visitors leave slow sites. Every second of waiting is a chance for someone to go back to the search results and pick a competitor.
• Paid ads: if you pay for traffic, a slow landing page wastes part of every click.

How to check your site

• Google Search Console shows a Core Web Vitals report based on real visitors, grouped into good, needs improvement and poor.
• PageSpeed Insights tests any page and shows both real-visitor data (when available) and a lab test with suggestions.
• Your hosting platform may offer real-user monitoring. Vercel’s Speed Insights, for example, reports these metrics for every page.

Test on mobile. That’s where most sites struggle, and it’s what Google looks at first.

The most common problems and fixes

Oversized images

The single most common cause of a slow LCP. Images should be resized for the screen, compressed and served in modern formats like WebP or AVIF. The main image should load first; images further down the page should load as the visitor scrolls.

Too many third-party scripts

Chat widgets, tracking tags, heatmaps and cookie banners all add weight and slow down interactions. Audit them regularly and remove anything nobody looks at.

Heavy themes and plugins

Many off-the-shelf themes load far more code than a page needs. On WordPress, plugin bloat is a frequent culprit.

Images and embeds without reserved space

If the page doesn’t know how big an image or advert will be, it jumps when it loads. Setting dimensions fixes most layout shift.

Web fonts

Fonts that load late can cause invisible text or a visible jump. Loading fewer font files, and loading them efficiently, helps.

Slow servers

If the server takes a long time to respond, everything else waits. Pre-building pages and serving them from a global network (a CDN) makes a big difference.

How good is good enough?

Aim for all three metrics in the green for most of your pages, on mobile. Beyond that, returns diminish for most business sites. I’ve taken a high-traffic platform to passing Core Web Vitals on every route, and the biggest wins almost always came from the basics above rather than anything exotic.

This site is built the same way. If yours is struggling, get in touch and we’ll tell you what’s slowing it down. And if you’re choosing a platform, our comparison of Next.js and WordPress covers how each handles performance.