A slow website does not frustrate visitors. It loses them. The distinction matters because frustration implies they stayed — they did not. According to consistent data across multiple studies, more than half of mobile visitors leave a page that takes longer than three seconds to load. They do not complain. They go somewhere else.
This is a business problem, not a technical one. The technical work required to fix it is real, but the reason to do it is not aesthetic or reputational. It is commercial.
What actually makes a site slow
Most slow websites share the same causes. In no particular order:
- Unoptimised images. A homepage hero image uploaded at 4MB when it could be 80KB is the single most common culprit. Image compression and modern formats (WebP, AVIF) are not optional.
- Unused JavaScript. Page builder plugins and theme frameworks often load megabytes of JavaScript for features that are not used on a given page. Every kilobyte has to be downloaded and parsed before the page renders.
- No caching. Without proper caching, every visitor request hits the server fresh. With it, most pages are served from memory.
- Cheap hosting. Shared hosting with a slow server response time sets a ceiling on performance that no amount of optimisation can fully overcome.
- Render-blocking resources. CSS and JavaScript loaded in ways that prevent the page from painting until they are fully processed.
Why Google cares and why you should too
Google’s Core Web Vitals — a set of page experience metrics including loading speed, visual stability, and interactivity — are a direct ranking signal. A slow site is penalised in search results. A fast site earns a structural advantage over slower competitors, all else being equal.
The SEO implication compounds the direct conversion implication. A slow site loses visitors who find it, and it is shown to fewer visitors in the first place. Both mechanisms point in the same direction.
What good looks like
A well-built site should score above 90 on Google’s PageSpeed Insights for both mobile and desktop. Largest Contentful Paint — the time until the main content is visible — should be under 2.5 seconds. Time to First Byte should be under 800ms.
These are achievable targets for almost any business website. They require deliberate work during the build, not heroic engineering after the fact.
Every site I build is performance-tested before launch. For existing sites that are slow, a performance audit is usually a half-day engagement with clear output. Get in touch if you want to know where your site stands.