A slow site is not an inconvenience, it is a cost. You pay for advertising at the moment someone arrives; the sale happens after the page has opened. Everyone lost in the two or three seconds in between has already been paid for.
In practice the cause is almost always in one of four places.
1. Images
The most common cause and the easiest to fix. The typical case: a photograph 4000 pixels wide and 6 megabytes heavy, placed in a slot 400 pixels wide. The browser downloads all 6 megabytes and only then shrinks the picture.
What to do:
- Prepare the image at the size it will actually be shown
- Move to
WebP— the same quality at a file two to three times smaller - Add
loading="lazy"to anything below the first screen
2. Fonts
Every extra family and every extra weight is a separate file. Three fonts at four weights is twelve files, all of which must arrive before the text appears.
Two families is enough. Take only the weights you use, not the full set. And font-display: swap shows the text before the font has arrived, so the visitor is not staring at an empty screen.
3. Third-party scripts
Analytics, a chat widget, a map, share buttons, a pixel, a banner. Each one calls its own server, and often your server waits for them.
The question is simple: what decision did this script influence in the last month? If there is no answer, remove it. Especially analytics that were installed once and never opened since.
4. Hosting
On the cheapest shared hosting, hundreds of sites share one server. Test at three in the morning and the site looks fast; test during working hours and it does not.
There is a way to check: measure at different times of day. If the spread is wide, the problem is the server, not the code.
How to measure it
With a number, not a feeling. PageSpeed Insights is free and measures by Google's own criteria — which means it shows you exactly what search takes into account.
Watch two figures: LCP (when the largest element appeared) should be under 2.5 seconds, and CLS (how much the page jumps while loading) under 0.1.
And read the mobile result, not the desktop one. Most of your visitors are on a phone, and mobile data is always slower than the office connection.
All four can usually be fixed without rebuilding the site. If the site is old enough that every fix breaks something else, that is a different conversation — and a redesign is usually the cheaper end of it.