Slow e-shop: how to speed it up — a practical guide

A slow site doesn't lose customers to a competitor's sale — it loses them earlier, before it even loads. Google's own data shows that every extra second of load time makes a mobile visitor dramatically more likely to leave. And because Google also factors speed into search rankings, a slow e-shop pays twice: fewer visitors arrive, and fewer of them buy. The good news: the biggest bottlenecks are almost always the same, and most can be fixed in an afternoon.

Measure first — on mobile

Before you fix anything, find out where you stand. Google evaluates websites by their mobile version (mobile-first indexing), so the mobile score is the one that matters — and it's usually 20–40 points worse than on desktop. You can measure with Google PageSpeed Insights, or more simply: the free EshopMedic mini check-up measures speed on mobile and desktop automatically, and checks for 15+ other types of errors while it's at it.

Three numbers that decide everything:

• LCP (main content load) — under 2.5 s is good, over 4 s is a problem. The usual culprit is a large image or a slider at the top of the page.
• CLS (layout shift) — the page must not "jump around" as images and ads load in. Target: under 0.1.
• Overall performance score — above 90 is excellent, 50–89 is average, below 50 speed is demonstrably costing you orders.

Checklist: what slows e-shops down most often

1. Huge images. The number one bottleneck by far. A phone photo can easily be 4–8 MB — it belongs on your site at the size it's actually displayed, in WebP format (any common editor or free online converter can produce it these days). Target: product photo under ~150 kB, banner under ~300 kB.
2. Too many third-party apps and widgets. Chat, heatmap, email pop-up, visitor counter, three tracking codes… every script has to load, and every one slows you down. Go through your installed add-ons and turn off everything you don't actively use — it's usually the fastest speed win with zero risk.
3. A full-width slider (carousel) on the homepage. Five banners in a rotator = five large images loaded right away, and almost everyone only ever clicks the first one anyway. A single good static banner is faster and usually sells better too.
4. Autoplaying videos. A background video looks impressive, but on mobile it costs seconds. Replace it with an image and make the video click-to-play (and host it on YouTube/Vimeo, not your own server).
5. Unused JavaScript and CSS. "Reduce unused JavaScript" warnings in your test results mean the page is loading code it doesn't need — typically leftovers from disabled apps or a heavy theme. On hosted platforms you can't do much about it directly, but cleaning up add-ons and switching to a leaner theme helps.
6. Web fonts. Every font weight (bold, italic…) is another file to download. Two weights are enough. Swap exotic fonts served from slow servers for system fonts or Google Fonts.
7. Links through redirect chains. A link goes http → https → www → final page: every redirect adds delay. Link straight to the final address (our check-up finds these for you).
8. Cheap, overloaded hosting. If "the server responds slowly" (TTFB over ~0.8 s), even perfect image optimization won't save you. On hosted platforms this isn't your problem; with WooCommerce/PrestaShop, consider a better plan or hosting specialized in e-commerce.
9. Missing lazy loading. Images below the fold should only load once the user scrolls to them. Modern themes handle this on their own — older ones don't, and happily load 60 photos at once on startup.
10. An old theme. Themes evolve — if yours is 5+ years old, a newer version from the same author is usually significantly faster. Back up your customizations before switching.

What order to fix things in

1. Measure your starting point (so you can see progress) — mobile and desktop.
2. Shrink the 10 largest images on your site (biggest impact for the least work).
3. Turn off unused apps, widgets, and tracking codes.
4. Fix the top of your homepage: one banner instead of a slider, no autoplay video.
5. Measure again. If you're still under 50 on mobile, tackle the theme or hosting.

Frequently asked questions