Why is your site slow? The 7 most common causes
A slow site costs you visitors and ad budget. The good news: the cause is usually one of the same seven things, and all of them can be fixed.
The short answer
Most slow sites don’t have one big problem. It’s the sum of large images, too many plugins or apps, a weak server and third-party code piling up on the page. Most of it can be fixed without rebuilding the site.
Measure first
Start with measurement, not guesses. Enter your address in Google PageSpeed Insights and look at the mobile result first. Google considers these thresholds “good”:
- LCP (main content load): 2.5 seconds or less
- INP (responsiveness): 200 milliseconds or less
- CLS (layout shift): 0.1 or less
1. Unoptimized images
A product photo shown 400 pixels wide on a phone can easily be uploaded at 4,000 pixels and several megabytes.
Resize images to the size they’re displayed at, use WebP or AVIF, and lazy-load anything below the fold.
2. Too many plugins or apps
Every WordPress plugin and every Shopify app can add its own code to the page. Remove what you don’t use; if two tools do the same job, keep one.
On Shopify, also check for code that uninstalled apps left behind in your theme.
3. A weak server or host
If the server is slow to respond, you’ve lost before the page even starts. On WordPress, a current PHP version, enough resources and a server close to your visitors make a real difference.
On Shopify the server side is handled for you, so focus on your theme and apps.
4. No caching or CDN
Caching stops the page from being rebuilt for every visitor; a CDN serves files from the location closest to them. On WordPress, a caching plugin plus a CDN such as Cloudflare gives most sites a noticeable boost.
5. A heavy theme or page builder
Do-everything themes load code for features you don’t use, and page builders can produce deeply nested layers. A lean theme or a block-based build can create the same design with far less code.
6. Third-party code
Live chat, ad pixels, heatmaps, review widgets… each looks small on its own, but together they can slow a page down badly. Keep what you really use, and remove or defer the rest.
7. Web fonts
Many font weights, and fonts loaded from another server, can delay your text from appearing. Load only the weights you use, serve fonts from your own server where possible, and use font-display: swap.
Where to start
Images and unnecessary plugins or apps usually have the biggest impact. If you’re not sure, our free 48-point inspection shows exactly where your site slows down, and what to fix first.
Free inspection
Where exactly is your site slowing down? We’ll tell you in 2 business days.
