Why is my WordPress website slow?

Most of the time, it's photographs. Somebody uploads twelve pictures straight off a phone, each one four thousand pixels wide, and the homepage now weighs more than a small film.

After that: too many plugins, hosting picked on price, no caching, and a theme built to do everything for everyone. You've read that list before. Work through it anyway, because it fixes most sites.

This post is about what you do when it's right and the site is still slow.

The boring answers

Images. A photo off a modern phone is enormous. WordPress makes smaller copies, but a lot of themes ignore them and serve the original anyway.

Plugins. Every one adds code to every page. The ones that hurt are the forgotten ones: a slider added for a Christmas promotion in 2022, a booking plugin from a system you stopped using, a chat widget nobody has answered in a year.

Hosting. Cheap shared hosting puts hundreds of websites on one machine. On a quiet day, you'll never notice, which is the problem, because the day you do notice is the day you're busy.

Caching and a CDN. Without caching, every visitor makes your server rebuild the page from scratch. A content delivery network keeps a copy nearer to whoever's looking, so somebody in Cornwall isn't waiting on a round trip to a data centre.

Fix that lot and most sites get quick. Some don't, and those are the interesting ones.

The company that was attacking its own website

Genius Division, the agency behind Better, launched a site for a large client. Fast hosting, images sorted, caching on, all by the book. Within hours, it was crawling.

Servers were fine. Cache was fine. Nothing in the usual places explained it.

Then somebody went through the server logs and found thousands of requests for one missing image. The same image, over and over, all day.

When the new site went live, the old files had been cleared out. Among them was an image used in the company's email signature. Every employee, every email, thousands of times a day, all asking a server for a picture that wasn't there any more. They were knocking their own website over with their signatures. Putting the image back fixed it that afternoon.

Nobody tells you to check your email signature when your website is slow.

Outlook clicking 170,000 links

Another one. A client sent an email campaign to 170,000 people at nine on a Tuesday morning, and the website immediately started running like treacle.

The obvious explanation is that everyone clicked at once. Except hardly anyone had opened it yet.

Outlook checks links in emails to see whether they're spam. It does that by following them. So the campaign went out, Microsoft's servers went and had a look on everyone's behalf, and the site took the lot in one go. The fix was to break the sends into chunks.

1,800 people in 30 seconds

A client went on Dragons' Den. Sunday night, prime slot, millions watching.

Everything was cached in advance and the server was ready. Craig sat there with the analytics open like it was a cup final. Ten people on the site. Show starts, they mention the business name, and thirty seconds later there are 1,800 people on it.

It held, and the server was being made bigger while it happened. A lot of websites would have fallen over on the spot, which is worth knowing if you've got anything coming up: a TV slot, a radio interview, a big campaign. That isn't gradual traffic arriving. It's a tap being opened.

When the speed tools say 95 and it still feels slow

DNS is the internet's phone book. Someone types your address, DNS says which machine to fetch it from. If that's set up badly, the browser sits there doing nothing before it even starts loading.

We've seen sites score 95 out of 100 on Google's tools while real people waited ten seconds for anything to appear. The test measures the page once it's found. It's a fast car with a flat tyre, and every guide about compressing images will send you the wrong way for a fortnight.

Rogue plugins do something similar: thousands of database queries per page, invisible to a speed score, obvious in the logs. A CDN set up wrong can make a site slower than having none at all.

What to check yourself

Open your site on your phone, on mobile data, away from the office wifi. That's how most people see it. Count the seconds properly, because three feels like ten when you're waiting.

Then have a look in the admin at the plugin list and ask what each one is for. Anything you can't answer for is a candidate. Check your homepage images and see whether any of them are wider than about two thousand pixels. Ask your host how many other sites share your server, and pay attention to how hard they find that question.

If all of that comes back clean and the site is still slow, stop. The remaining causes live in logs and DNS records, and guessing at them costs more time than paying someone who has seen them before.

What we do about it

Performance monitoring on every plan means we see a page getting slower before you do, rather than finding out when somebody complains. Better+ adds the deeper monthly look: Search Console, GTmetrix, PageSpeed and Semrush read together, which is the only way to tell a real problem from a bad afternoon on one tool.

Hosting is on every plan too, with a content delivery network, because half of what makes a WordPress site slow is underneath WordPress. The WordPress hosting page covers how that side works, and what maintenance includes has the rest.

Nobody hands you a prize for a fast website. What you avoid is people leaving before the page appears, and ad budget spent on visitors who never saw it. None of them ring to tell you either.