A slow website is easy to spot: open it on a phone, on mobile data, and count. If nothing happens for two seconds, some of your visitors are already gone.
This article is about what makes websites slow, written without jargon. Most of the causes are not technical, even though they look it.
What is actually being measured
When somebody says a site is slow, they usually mean one of three things:
- How long until anything appears. A white screen.
- How long until the main thing appears. The headline, the hero image.
- Whether it jumps around while loading. You go to click and the content moves, because an ad or an image without dimensions just arrived.
The third one annoys people most and gets measured least. A jumping page feels broken even when it is fast.
The four usual causes
1. Images
By far the most common and the easiest to fix. A photo straight off a camera can be 6 MB. On a website it should be 200 kB.
The fix is boring and it always works: resize to the dimensions it is actually displayed at, save it in a modern format, and load it only when somebody scrolls to it.
If your site has one speed problem, it is almost certainly this one.
2. Scripts you forgot about
Chat, cookie banner, analytics, remarketing pixel, map, reviews widget, counter, A/B testing.
Somebody added each of these for a good reason. Together they can outweigh the entire rest of the site. And they are insidious, because you install them once and then nobody ever looks again.
Audit them once a year. You will almost always find at least one that should not be there.
3. Fonts
A custom font has to download, and until it does, text is either invisible or it reflows once it arrives and the page jumps.
You do not have to give it up. Load only the weights you use, and only the characters you need.
4. A template that does everything
A general purpose template carries the code for every feature it offers, including the ninety percent you never use. On a brochure site that does not matter. On a shop with a large catalogue it is money.
Why this is not just a feeling
Site speed affects how many people reach checkout, and it is one of the signals search engines take into account. Nobody can tell you the exact weight, and anyone who claims otherwise is guessing.
But even if it had no effect on search at all, the first part still holds: a slow site loses people who had already decided to come.
How to measure it yourself
Open PageSpeed Insights, paste your address, and switch to mobile. Not desktop. Almost all your visitors are on a phone and on a worse connection than you have at your desk.
Do not treat the score as a grade. The interesting part is the list underneath, which names what is actually holding it up. If the top entry is about images, see above.
Then run the best test of all: open your own site on your phone, on mobile data, outdoors. Not on the office wifi.
What can be fixed and what cannot
Images, scripts and fonts can be fixed on almost any site without rebuilding it. It is usually the best ratio of effort to result available on an existing site.
What cannot be fixed: a site built on foundations that are slow in themselves. There you can reach a decent result, not a great one. You will recognise it because after fixing images and scripts nothing much changes.
At that point the question is whether to keep polishing or put the money into a new site. The answer depends on how much the site earns you, not on how old it is. If you are not sure which group your site falls into, send me its address through the form and I will take a look.