Your website is slow. You've tested it, seen the poor scores, and now you're wondering: what's actually causing this? Here are the most common culprits - and what you can do about each one.
1. Massive Images
The problem: This is, by far, the most common cause of slow websites.
Photos uploaded straight from your camera or phone can be 5-10MB each. Your homepage hero image doesn't need to be 4000 pixels wide. Your team photos don't need to be printable at poster size.
Real example: A 4MB hero image takes 4 seconds to load on a 4G connection. That same image, properly optimised, might be 150KB and load in under a second.
How to spot it: PageSpeed Insights will flag "Properly size images" or "Serve images in next-gen formats" as opportunities.
The fix:
- Resize images to the dimensions they'll actually display at
- Compress images before uploading (TinyPNG, Squoosh, ShortPixel)
- Use modern formats like WebP instead of PNG or JPEG
- Consider lazy loading for images below the fold
Can you fix it yourself? Yes - this is the easiest win. Compress images before uploading. Most people can reduce image sizes by 70-90% with no visible quality loss.
2. Cheap Hosting
The problem: Budget hosting providers cram hundreds of websites onto single servers. When any of those sites gets busy, everyone slows down.
The first thing that happens when someone visits your site is their browser requests the page from your server. If your server is slow to respond (high "Time to First Byte" or TTFB), everything else is delayed too.
How to spot it: If your TTFB is over 600ms in PageSpeed Insights, hosting may be the issue. Also check if speed varies dramatically at different times of day.
The fix:
- Upgrade to quality hosting (expect to pay £15-30/month for business sites)
- Consider managed WordPress hosting if you're on WordPress
- Look for hosts with UK data centres if serving UK customers
- Ask about server specs and how many sites share your server
Can you fix it yourself? Changing hosts is straightforward but requires some technical confidence. Most good hosts offer migration assistance.
3. Too Many Plugins or Apps
The problem: Every plugin adds code that needs to load. Even inactive plugins can cause issues. Some plugins are well-coded and light; others are bloated nightmares that load scripts on every page whether needed or not.
WordPress is particularly prone to this. It's easy to install plugins for everything, and many themes come with dozens of features you never use.
How to spot it: On WordPress, go to Plugins and count. More than 20 active plugins is a red flag. Also look for plugins with poor reviews or that haven't been updated in years.
The fix:
- Audit your plugins - do you actually use each one?
- Delete (not just deactivate) plugins you don't need
- Choose multipurpose plugins over many single-purpose ones
- Check if features can be done with less resource-heavy alternatives
Can you fix it yourself? Yes - this is maintenance you should do regularly. Just be careful deleting plugins you're unsure about; back up first.
4. Third-Party Scripts and Widgets
The problem: Every external service you add loads from their servers. Chat widgets, analytics, booking systems, social media feeds, review widgets, cookie consent banners - each one adds requests and processing time.
The worst offenders often load their own additional resources, creating a chain of slowness.
How to spot it: In GTmetrix's waterfall, look for long bars from external domains (anything that's not your website's URL).
The fix:
- Be ruthless about what you add - does it provide real value?
- Remove social feeds (people can click a link to your profiles)
- Consider whether you need that chat widget on every page
- Use lightweight alternatives where possible (Fathom/Plausible instead of Google Analytics)
Can you fix it yourself? Usually yes - it's a matter of removing code or disabling features.
5. Bloated Website Builders
The problem: Drag-and-drop website builders (Wix, Squarespace, some WordPress themes) add significant code to enable their editing interfaces. You pay for simplicity with speed.
This is hard to fix because it's built into the platform.
Real talk: Wix and Squarespace have improved significantly in recent years. Most score 50-75 on mobile - acceptable, if not excellent. But they have a speed ceiling you can't break through.
How to spot it: If you've optimised everything else and still can't break 70 on mobile, your platform may be the limiting factor.
The fix:
- Accept the trade-off (simplicity vs maximum speed)
- Move to a faster platform if speed is critical (custom build, lightweight WordPress, static site generators)
- Ensure you're not making things worse with additional plugins/apps
Can you fix it yourself? Within a platform, options are limited. Migrating to a new platform typically requires professional help.
6. Web Fonts
The problem: Custom fonts need to download before text can display properly. Multiple font weights (regular, bold, italic) multiply the problem.
Worse, some implementations block text from showing entirely until fonts load - creating a Flash of Invisible Text (FOIT).
How to spot it: If text appears delayed or changes appearance as the page loads, fonts may be the issue.
The fix:
- Limit yourself to 2-3 font weights
- Use
font-display: swapto show fallback fonts while loading - Consider system fonts (they don't need to download)
- Host fonts locally instead of loading from Google Fonts
Can you fix it yourself? Partially - reducing font weights is easy. The technical fixes typically need a developer.
7. Render-Blocking Resources
The problem: Some code blocks the page from rendering until it's fully loaded. This often includes:
- CSS files in the document head
- JavaScript files that aren't deferred
- Synchronously-loaded third-party scripts
How to spot it: PageSpeed Insights explicitly flags "Eliminate render-blocking resources."
The fix:
- Defer non-critical JavaScript
- Inline critical CSS
- Load scripts asynchronously where possible
- Move scripts to the bottom of the page
Can you fix it yourself? This typically requires developer intervention or specific plugin settings.
8. No Caching
The problem: Without caching, every visit requires loading every resource fresh from the server. With proper caching, returning visitors load much of the page from their browser's stored files.
How to spot it: PageSpeed Insights flags "Serve static assets with an efficient cache policy."
The fix:
- Enable browser caching (server configuration)
- Use a caching plugin on WordPress (WP Rocket, W3 Total Cache)
- Configure cache headers properly
- Consider a CDN for global visitors
Can you fix it yourself? If using WordPress, caching plugins are straightforward. Server-level configuration typically needs professional help.
9. No CDN (Content Delivery Network)
The problem: If your server is in London but your visitor is in Edinburgh, every request travels that distance. A CDN stores copies of your content in multiple locations, serving visitors from the nearest one.
How to spot it: Long load times for visitors in different geographic regions. TTFB that varies by location.
The fix:
- Add a CDN like Cloudflare (has a free tier)
- Use a host that includes CDN functionality
- Enable CDN features in your caching plugin
Can you fix it yourself? Cloudflare's basic setup is manageable. Full CDN configuration typically needs professional help.
Quick Diagnosis Checklist
Run through this list when investigating slow performance:
- Test with PageSpeed Insights - Get your baseline scores and see what's flagged
- Check your largest images - Are any over 500KB? Over 200KB?
- Count your plugins - More than 15? Time to audit.
- List your third-party scripts - Chat, analytics, social, tracking - add them up
- Check your hosting - When did you last consider upgrading?
- Test on mobile data - Visit your site on your phone without WiFi
The 80/20 of Website Speed
If you only fix three things, fix these:
- Compress and resize your images - Often produces the biggest single improvement
- Remove unused plugins and scripts - Clean out the cruft
- Get better hosting - The foundation everything else sits on
These three changes address the majority of speed issues for most small business websites.
The Bottom Line
Slow websites are rarely caused by one thing. It's usually a combination of factors: oversized images, too many plugins, cheap hosting, and accumulated third-party scripts.
Start with the easy wins - image compression and plugin cleanup. Then consider hosting. If you've addressed all of these and still have problems, it may be time for professional help or a platform change.
Speed matters for both user experience and search rankings. But the good news is that most issues are fixable, and the improvements are often dramatic.