Why speed matters
A slow website costs you in three ways:
- visitors give up before they see your offer, especially on phones,
- fewer people send a form or finish checkout, because every next step is slow too,
- Google takes speed into account when ranking results. It isn’t the most important factor, but with similar content the faster site has the edge.
Speed isn’t just the first load. It also matters whether the page responds to clicks straight away and whether elements jump around while it loads.
How to check your site
The simplest tool is Google’s free PageSpeed Insights – pagespeed.web.dev. Enter your address and wait for the result. The report has two parts:
- Data from real visits (at the top): measurements from the browsers of people who visited the site in the last 28 days. This is what counts for Google. Sites with little traffic may not have this section.
- Diagnostics (below): a one-off test under simulated conditions, with a score from 0 to 100 and a list of recommendations. Useful for finding causes, but the score itself can vary between runs.
A few tips:
- look at the mobile result first, as it’s usually worse and applies to most visitors,
- test not just the home page but also the pages customers land on: your offer, a product page, contact,
- if you have Google Search Console, the “Core Web Vitals” report shows which groups of pages need work.
Don’t chase 100. A 100/100 diagnostics score isn’t a goal in itself. What matters more is that the data from real visits is in the green range.
Core Web Vitals in a nutshell
Google rates user experience with three metrics:
| Metric | What it measures | Good result |
|---|---|---|
| LCP (Largest Contentful Paint) | how fast the main content appears, e.g. a large photo or heading | up to 2.5 s |
| INP (Interaction to Next Paint) | how fast the page responds to a click or tap | up to 200 ms |
| CLS (Cumulative Layout Shift) | whether elements shift while the page loads | up to 0.1 |
A result counts as good when it stays within these limits for at least three out of four visits.
What slows sites down most often
On WordPress sites the causes repeat surprisingly often:
- Oversized images. A photo straight from a camera weighs several megabytes, yet on a phone screen it’s shown a few hundred pixels wide. Modern formats (WebP, AVIF) and proper sizes can make a page several times lighter.
- No caching. Without it, the server builds the page from the database on every visit. With caching, it sends a ready-made file.
- Too many plugins and scripts. Every plugin can add its own files to every page, even where it isn’t needed. The same goes for chats, maps, social media widgets and tracking codes.
- A heavy theme or page builder. Feature-rich page builders produce a lot of code even for simple layouts.
- Weak hosting and an old PHP version. The cheapest shared hosting can be a bottleneck, and newer PHP versions are noticeably faster.
- Sliders and videos at the top of the page. A large image carousel or background video is often the biggest element on the page and the main reason for a poor LCP.
Where to start
Not every fix pays off equally. Usually the most gain comes from, in this order:
- Image optimisation: resizing, compression and modern formats, including for images added in the past.
- Caching: at server level or with a proven plugin, set up so it doesn’t break forms and the cart.
- A plugin and script review: removing unused ones and limiting the rest to the pages that need them.
- A current PHP version and, if needed, better hosting.
- Only last, replacing the theme or page builder, if that’s the main problem.
Make a backup before bigger changes. More on that in the article on website backups.
Beware of “plugins that speed up everything”
Optimisation plugins can help, but switched on blindly they often do harm: they combine and defer scripts in ways that break menus, forms or the cart. Several such plugins at once is a short road to bugs that are hard to track down. After every change, check the key features of your site, ideally on a phone too.
Checklist
- I’ve checked the home page and key pages in PageSpeed Insights, on mobile.
- I know whether the data from real visits is in the green range.
- Images are sized to the screen and use a modern format.
- The site uses caching.
- I’ve removed plugins I don’t use.
- The server runs a current, supported PHP version.
- After changes, I’ve checked forms, the menu and the cart on a phone.
