Why a 1-second delay is costing you customers

What Core Web Vitals actually measure

Google's Core Web Vitals distil site experience into three numbers. Largest Contentful Paint (LCP) measures how quickly the main content appears. Interaction to Next Paint (INP) measures how fast the page responds when someone taps or clicks. Cumulative Layout Shift (CLS) measures how much the page jumps around as it loads. Together they describe what a real human actually feels — and Google uses them in ranking, so they affect both how many people find you and how many stay.

The conversion link is psychological

Users don't run a stopwatch; they form an instant impression. A site that paints fast and stays stable feels trustworthy and well-run. One that's slow and janky feels broken, and people extend that feeling to the business behind it. Nobody emails to say 'I left because your hero image took four seconds' — they just leave, and you never hear about the sale you didn't make.

Slow pages punish paid traffic twice

This is where it really hurts if you run ads. First, you pay for every click, so a visitor who bounces on a slow page is spend you'll never recover. Second, Google and Meta both factor landing-page experience into ad quality and cost — a sluggish page quietly raises your cost per click and shrinks your reach. You end up paying more to send people to a page that converts less. Fixing speed lowers your effective cost per acquisition on both fronts.

Mobile is where it bites hardest

Most paid traffic is mobile, on mid-range phones and patchy connections — a world away from the fast laptop your site was probably tested on. A page that feels fine in the office can be painfully slow in the real world. We always judge performance on throttled mobile, because that's where the majority of your customers actually are.

How we fix it

Treat speed as a feature with a budget, not an afterthought. That means a modern framework, lean JavaScript, properly sized and lazy-loaded images, optimised fonts, and caching at the edge. We set a performance budget per page and protect it on every release, so the site doesn't quietly get heavier over time as features and tags pile up.

Measure it where it counts

Lab tools like Lighthouse are useful, but the truth lives in field data — what real users experience, visible in Google Search Console's Core Web Vitals report and your analytics. Watch the trend, tie it to conversion rate, and you'll quickly see the speed work pay for itself in pounds, not just points.

If your site loads slowly, you're buying traffic that bounces and paying a premium to do it. For most businesses, fixing speed is the highest-ROI improvement available — no new campaigns, no bigger budget, just more of the visitors you already pay for turning into customers.