If your page is slow, the visitor doesn’t wait around to find out why. They leave. And on mobile — where most traffic comes from — they leave even faster.
The good news: across the WordPress sites we see, the causes repeat. They’re not mysteries. There are seven of them, and most are fixable without rebuilding the site from scratch.
1. Too many plugins — and often duplicates
This is cause number one. Every plugin loads its own files on every page, even where it isn’t used.
The worst pattern is duplicates: two plugins doing the same job. We’ve seen it repeatedly — two different email plugins, two analytics plugins, on the same site. On an e-shop we took on, rationalising the plugins meant 16 fewer plugins, and with them nearly 7,000 files that were loading for no reason.
You don’t need to remove them all. You need to know which and why.
2. The theme does far more than you need
The market’s “multipurpose” themes sell on the promise that they do everything. That’s precisely the problem: to do everything, they load everything — on every page, whether you use it or not.
The same applies to page builders. They’re convenient for editing, but they add layers of code. That isn’t always the wrong choice — you just need to know the cost.
3. Images nobody has touched
A 4,000-pixel photo uploaded straight off a phone, to be displayed in a 400-pixel frame, carries tens of times more data than it needs to — the visitor downloads the whole photo and the browser then shrinks it. Multiply that by 30 products.
Two things solve 90% of it: correct dimensions and a modern format (WebP/AVIF). On one e-shop, the main homepage image dropped from 277 KB to 64 KB — same image, same quality to the eye, a quarter of the weight.
4. Dozens of separate CSS and JavaScript files
Every file is a separate request to the server. The problem isn’t the size — it’s the count.
On an e-shop we optimised, we measured 53 separate CSS files. After combining them, one. And the page’s total requests dropped from 157 to 115.
5. No caching — or caching set up wrong
Without a cache, the server rebuilds the page from scratch for every visitor: runs code, queries the database, assembles the result. With caching done right, it already has it ready and just sends it.
The difference is dramatic and measurable. On the e-shop mentioned above, server response time dropped from ~820 milliseconds to ~20 — roughly 40 times faster. That’s before the page even starts downloading; it’s the time your visitor spends staring at a white screen.
An honest note on these numbers: every measurement in this article comes from the same e-shop, before and after the optimisation phase — same build, same method. We are not comparing “old site vs new site”, because that would be an unfair comparison.
6. Hosting that can’t keep up
Cheap shared hosting splits the same server across dozens of sites. When your neighbour gets busy, you get slow. And it often runs outdated software versions.
You don’t always need to switch provider. But if the server responds slowly even on an empty page, no amount of optimisation will save you.
7. An outdated PHP version — the most neglected of all
PHP is the language WordPress runs on. Newer versions are noticeably faster than old ones, and upgrading is often the cheapest improvement available.
There’s a more serious side too: old versions stop receiving security updates. On a corporate site we took on, PHP was on a version that is no longer supported — we moved it to a current one. This isn’t only about speed; it’s an open door.
How to work out which one is your problem
Don’t buy a solution before you know the cause. The order is:
- Measure. Run your site through Google PageSpeed Insights. Look at when the main content appears (LCP) and how much elements shift (CLS) — on mobile, not desktop.
- Separate the causes. Slow server, or heavy page? Those are different problems with different price tags.
- Fix in order of cost-to-benefit. Caching and images first — cheap and immediate. Plugins and theme after.
- Measure again. Without a before and an after, you don’t know whether you paid for anything.
And a warning: don’t chase 100/100. It’s a lab score, not sales. Going from 40 to 80 changes the visitor’s experience; going from 90 to 100 usually costs more than it’s worth.
Want to see what’s slowing your site down?
Send us its address and we’ll tell you for free what’s holding it back — speed, security, mobile display. With no obligation whatsoever.
If the site is structurally healthy, we’ll say so: it needs optimisation, not a new site. If it rests on things nobody maintains any more, we’ll explain why a rebuild works out cheaper in the long run. If your site is an e-shop, see the e-shop, speed & SEO service.
Either way, you’ll know why — and anything we take on comes with a fixed price and a written delivery date.