Why is my website so slow, and what can I fix myself?

The usual causes, most common first

• Oversized images. A photo straight from a phone or camera can be 5 MB or more and several thousand pixels wide, when the page needs a fraction of that. Large banner images and sliders at the top of the page do the most damage.
• Too many apps or plugins. Each one can add its own scripts and styles to every page, including pages where it is not used.
• Third-party scripts. Live chat, pop-ups, review widgets, embedded social feeds, video embeds, heat maps and advertising pixels all load from other companies’ servers and compete with your own content.
• Hosting. This applies mainly to WordPress. Low-cost shared hosting, an old PHP version and no caching all make the server slow to respond. Shopify, Wix and Squarespace run the hosting for you, so on those platforms the cause is nearly always what is on the page.

How to test your site with PageSpeed Insights

1. Go to pagespeed.web.dev, paste in your home page address and select Analyse.
2. Look at the Mobile tab first. Most visitors are on phones, and the mobile test uses a slower connection, so it shows problems more clearly.
3. If the top of the report shows data from real users, check the three Core Web Vitals. Google’s targets are a Largest Contentful Paint of 2.5 seconds or less, an Interaction to Next Paint of 200 milliseconds or less, and a Cumulative Layout Shift of 0.1 or less.
4. Scroll to the diagnostics list. Items about image size, unused JavaScript and third-party code point to the causes above. The report names the specific files involved.
5. Repeat the test for a product or service page, and save the results so that you can compare after making changes.

The score out of 100 changes a little each time you run the test, so compare the measurements in seconds and not only the score.

Fixes a non-technical owner can do safely

• Resize images before uploading them. Around 2,000 pixels wide is enough for a full-width banner, and 1,000 to 1,200 pixels is enough for most product and content images.
• Compress images with a free tool such as Squoosh or TinyPNG. Use JPEG or WebP for photographs and keep PNG for logos and graphics that need a transparent background. Aim for well under 300 KB for most images.
• Reduce home page sliders to a single image. Each extra slide is another large file that most visitors never see.
• Remove apps, plugins and widgets you no longer use, including old pop-up, chat and review tools.
• Replace embedded videos near the top of the page with a still image that links to the video, or move them further down.

On Shopify, uninstalling an app does not always remove the code it added to your theme. If PageSpeed Insights still lists files from an app you have removed, the leftover code needs to be taken out of the theme. Duplicate the theme before anyone edits its code.

WordPress-specific improvements

1. Take a full backup of files and database before changing anything.
2. Install one caching plugin. Caching saves a ready-made copy of each page so the server does not rebuild it for every visitor. WP Super Cache and W3 Total Cache are free, LiteSpeed Cache is the right choice if your host uses LiteSpeed servers, and WP Rocket is a paid option. Never run two caching plugins together.
3. Add an image optimisation plugin such as ShortPixel, Imagify or EWWW Image Optimizer to compress existing images and serve WebP versions.
4. Check your PHP version in the hosting control panel. Current 8.x versions are noticeably faster than old 7.x versions. Ask your host before switching, and test the site straight afterwards, because very old plugins can break.
5. Test the site after each change, including the contact form and the checkout, so that you know which change caused any problem.

If the report shows a slow server response time even with caching switched on, the hosting is the limit. Moving from a low-cost shared plan to a better-specified one often makes more difference than any plugin.

What to leave to a developer

• Editing theme code to remove leftover app scripts or to delay scripts until they are needed.
• Settings in caching plugins that combine, minify or defer JavaScript and CSS. These can break menus, sliders and checkouts, and the damage is not always obvious straight away.
• Changes to tracking tags and Google Tag Manager, where a mistake can quietly stop your sales tracking.
• Moving a WordPress site to new hosting, which involves the database, email and DNS.

Related questions

What is a good PageSpeed Insights score?

Google labels 90 and above as good and 50 to 89 as needing improvement. For a small business site, passing the Core Web Vitals on mobile matters more than the exact number.

Does a slow website affect my Google ranking?

Page experience, including Core Web Vitals, is one of many signals Google uses, so speed can make a difference between similar pages. The more direct effect is on visitors, who are more likely to leave a page that is slow to appear.

Will removing apps or plugins break my site?

It can if the site depends on them, so check what each one does before removing it. On WordPress, take a backup and deactivate the plugin first to see the effect before deleting it. On Shopify, check whether the app has a block or embed switched on in your theme before uninstalling.