Almost every slow website we look at is slow for one of four reasons, and almost none of them are the reason the owner expects. People arrive convinced they need better hosting. Usually they need to stop shipping a 4MB photograph.
Here is what actually costs you time, roughly in the order it tends to matter.
1. Images, nearly always
On the sites we audit, images are routinely 70–90% of total page weight. A photo straight off a phone or a stock library is often 3–5MB. Displayed in a 600px-wide slot on a page, roughly 95% of that data was downloaded for nothing.
Three things fix most of it:
- Resize before uploading. If the largest it will ever display is 1200px wide, do not upload 4000px.
- Use a modern format. WebP is typically 25–35% smaller than an equivalent JPEG at the same visual quality.
- Lazy-load anything below the fold — but not your hero image. Lazy-loading the first thing on screen delays the exact element the browser measures your speed by.
That last point catches people out constantly. A plugin that lazy-loads everything, including the hero, will make your scores worse rather than better.
2. Plugins you forgot you installed
Every active plugin can add CSS and JavaScript to every page — including pages that have nothing to do with it. A form plugin often loads its stylesheet on your blog posts. A slider plugin loads on pages with no slider.
Go through the plugin list and be unsentimental. If you cannot name what a plugin does and where it does it, you probably are not using it.
3. Fonts
Fonts are small but they block. If a font file has to download before text can render, visitors see nothing where your headline should be.
Load two families at most, and only the weights you actually use — loading nine weights of a family when the design uses two is a common and expensive habit. Add preconnect hints for the font host, and use font-display: swap so text is visible in a fallback while the real font arrives.
4. Hosting — but later than you think
Hosting matters, and cheap shared hosting genuinely is slow. But it is fourth on this list because moving a 6MB page to a faster server gives you a faster 6MB page. Fix the weight first, then judge the host.
What about the score out of 100?
PageSpeed Insights is a useful diagnostic and a terrible target. It is easy to chase a green number with changes that make the actual experience worse — deferring scripts the page needs, or lazy-loading content people immediately look for.
Optimise for what a person on a phone on mobile data experiences. The score usually follows; when it does not, trust the person.
The three numbers worth watching are Core Web Vitals: how quickly the main content appears (LCP), whether the layout jumps while loading (CLS), and how quickly the page responds when tapped (INP). Those measure things a visitor can actually feel.
The one that costs nothing
Set width and height on every image. It does not make anything download faster, but it tells the browser how much space to reserve, so the page stops jumping around as images arrive. Layout shift is one of the most irritating things a site can do to someone, and this is a one-line fix per image.
Where to start
Run one page through PageSpeed Insights and look only at the opportunities list, largest saving first. Nine times out of ten the top item is an image. Fix that, re-run, repeat. You will get most of the available improvement before you touch anything technical.
If you have worked through all of that and the site is still slow, the problem is more likely the build itself than any single asset — and that is worth a proper look rather than another plugin.
