Your store might load quickly on your laptop and still be slow on mobile. Mobile devices have slower processors and less reliable connections, so problems that are invisible on desktop become obvious. These are the usual suspects, roughly in order of how often we find them.
1. Oversized images
Uploading a 4,000-pixel photo and letting the browser shrink it is the most common cause of slow pages.
Fix: serve modern formats such as WebP or AVIF, resize images to the size they are shown at, and lazy-load images below the fold. Do not lazy-load the main product image, as it should appear immediately.
2. Too many apps and plugins
Every review widget, pop-up, chat tool and tracking script adds code that the phone has to download and run.
Fix: list every app and script, note what each one does for you, and remove the ones you no longer need. Load the rest only on the pages that use them.
3. Heavy themes and page builders
Some themes load sliders, animations and fonts on every page, whether they are used or not.
Fix: use a lightweight theme, limit custom fonts to one or two weights, and avoid auto-playing sliders. If the theme itself is the problem, a redesign can be the faster fix.
4. Third-party scripts loading first
Chat widgets and marketing tags that load before your content make the page feel frozen.
Fix: defer non-essential scripts until after the page has loaded, or until the visitor interacts.
5. Slow hosting or no caching
If the server is slow to respond, nothing else can start.
Fix: use good hosting, page caching and a content delivery network (CDN), especially if you sell internationally.
How to measure it
Run your key templates, such as the home page, a category page and a product page, through PageSpeed Insights and focus on the Core Web Vitals:
- Largest Contentful Paint: how quickly the main content appears
- Interaction to Next Paint: how quickly the page responds to taps
- Cumulative Layout Shift: whether things jump around while loading
Test on a real mid-range phone as well. It tells you more than any score.
Speed improvements tend to help conversions and search visibility at the same time. If you want the fixes done for you, see our speed optimisation service.
