Why is my WordPress site slow? Seven common causes

First, measure it

Run your page through PageSpeed Insights, a free tool from Google, and look at the mobile result, not just desktop. Read the list of opportunities it gives you rather than focusing on the score alone. Test your home page and one inner page, because they often have different problems.

Seven common causes

• Oversized images. Photos straight from a camera or a stock site can be several megabytes. Resize them to the size they're shown at, compress them, and use a modern format such as WebP.
• Too many plugins. Each plugin can add scripts and styles to every page. Remove the ones you don't use, and check whether two of them do the same job.
• A heavy theme or page builder. Some themes load a lot of code for features you never use. This is one of the harder problems to fix without changing the design.
• No caching. Without caching, WordPress builds each page from scratch for every visitor. A good caching setup serves a ready-made copy instead.
• Slow hosting. An overloaded server is slow whatever you do on the site. If the server takes a long time to start responding at all, that's a hosting problem.
• Third-party scripts. Chat widgets, tracking tags, social feeds and ad scripts each add requests. Keep only what you really use.
• Web fonts and sliders. Lots of font files, or a full-width image slider at the top of the page, can delay the first thing visitors see.

How to find the one that's hurting you

Change one thing at a time and measure again. Deactivate a plugin on a staging copy of the site, run the test and compare. The Network tab in your browser's developer tools shows which files are the biggest and the slowest. It's dull work, but it's how you stop guessing.

What you can fix yourself, and what needs a developer

You can usually handle image compression, deleting unused plugins and themes, and keeping everything updated. A developer is worth it for theme or builder bloat, database clean-up, custom code, server settings, and layout shifts that make the page jump as it loads.

A note on scores

Don't chase a perfect number. A site that feels quick on a real phone and passes Core Web Vitals is a success, even if one tool still gives it a 90.

A sensible order to work in

• Measure the home page and one inner page on mobile, and save the results.
• Fix the images first. It's the cheapest change and often the biggest.
• Remove plugins and themes you don't use, then update the ones you keep.
• Set up caching, and check the result on a real phone as well as in a tool.
• Test again. If the site is still slow, look at the theme, the hosting and third-party scripts.