Why your website is slow: 5 causes and the fix for each
Every slow site we’ve audited fails in a predictable set of ways. Here’s the list, ranked by how often it’s the culprit.
We audit a lot of slow sites. The causes cluster around a handful of specific, predictable issues. Work through this list in order; the average SME site gets a 40-point Lighthouse lift from the first three alone.
1. Un-optimised hero image
The biggest above-the-fold image is almost always your LCP element — the number Google actually ranks you on. If it’s a 3MB JPG served straight from WordPress uploads, you’ve lost before you’ve started. Fix: serve AVIF with JPG fallback, set explicit width/height, add a preload link in the head. Target: under 200KB for the hero.
2. Google Tag Manager with everything in it
A typical SME GTM container has GA4, Meta Pixel, LinkedIn Insight, a review widget, a live chat loader, and whatever the last agency installed and didn’t clean up. Each is a third-party script blocking the main thread. Fix: audit GTM, remove what’s not actively attributing revenue, load the rest with ‘async’ or ‘defer’ and behind consent where legally required.
3. Web fonts loaded synchronously
Font files are heavy and, by default, block text rendering. You get a visual blank for 200–1,500ms while the font downloads. Fix: use `font-display: swap`, subset to Latin, preload the critical font file, and ideally self-host instead of relying on Google Fonts.
4. Bad hosting region
A UK business on a US-region shared host pays a 90–150ms TTFB tax on every single request. Multiply by six assets and you’ve lost a second before the browser starts painting. Fix: move to a host with an edge network, or at minimum to a server in the country where most of your traffic lives.
5. Too many plugins (WordPress, specifically)
Every plugin you install ships its own CSS, JS, and often its own SQL queries on every page load. Twenty plugins later, your homepage is shipping 2MB of JavaScript for a site with no interactivity. Fix: audit the list, uninstall anything that isn’t earning its weight, and replace page-builder plugins with native block patterns where possible.
“Slow sites aren’t slow because of magic. They’re slow because four or five specific things got skipped at build time.”
How to measure it
- PageSpeed Insights — lab + field scores, plus specific fixes.
- Chrome DevTools Lighthouse — more detail, live on your machine.
- WebPageTest.org — waterfall view, finds blocking resources.
Run all three. If any of them shows LCP over 2.5s or INP over 200ms, you have work to do.
What’s baked into every Stratevo build
Every site we ship goes through a Lighthouse + accessibility audit before launch — we don’t hand you a slow site and tell you to fix it later. Hero images served as AVIF with explicit dimensions; tag manager scoped to what you actually use; web fonts subset, swapped, and self-hosted; edge hosting close to your audience; no plugin sprawl because there are no plugins. Lighthouse scores ship in the 90s as standard, not as an upgrade.
If your current site is failing this audit, the fastest path to a passing one is a rebuild on our subscription. From £89/mo, live in 7 days. Or talk to us about a one-off performance audit if you just want the fix list.