How-to · 7 min read
Why is a Shopify store slow — and how to check
A slow store is an expensive store. Shoppers abandon pages that take more than a few seconds to load, and Google factors speed into rankings. Whether it's your own store feeling sluggish or a competitor's you're studying, the causes are usually the same handful of culprits — and most are fixable. Here's how to diagnose the problem and what to do about it.
How to actually measure it first
Don't guess from feel — measure. Run the store's URL through Google's PageSpeed Insights (free). It gives you a score for mobile and desktop plus a specific list of what's slowing the page down. Test the mobile score especially, since most storefront traffic is mobile and mobile is where slowness hurts most. That report turns "it feels slow" into a concrete list of causes you can work through.
Culprit 1: too many apps
This is the most common cause by far. Every app a store installs usually adds JavaScript that loads on every page — and it keeps loading even after you stop using the app. A store that has installed and "removed" twenty apps over its life often still carries leftover code from many of them. Scan the store's apps with the app detector to see how many are actually running. If the list is long, app bloat is almost certainly part of the problem. The fix: audit every app, remove the ones that aren't earning their keep, and check that removed apps didn't leave code behind.
Count a store's apps
See how many apps are loading — a common speed culprit.
Culprit 2: huge, unoptimised images
Images are usually the heaviest thing on a page. A store that uploads 4000-pixel product photos straight from a camera forces every visitor to download enormous files. The fix is straightforward: compress images before uploading, use appropriately sized dimensions (you rarely need more than ~2000px wide), and let Shopify serve modern formats. A single oversized hero image can add whole seconds to a page load on mobile.
Culprit 3: the theme
Themes vary a lot in how lean they are. Older themes, or heavily modified ones with lots of custom code piled on over the years, can be slow by design. Shopify's own Dawn theme is one of the leanest available, which is part of why it's the default. Check what theme a store runs with the theme detector — if it's an older or heavily bloated theme, that's a structural cause of slowness that no amount of image tweaking fully fixes. Sometimes the real answer is migrating to a faster, modern theme.
Culprit 4: too many fonts and third-party scripts
Custom fonts, chat widgets, review popups, tracking scripts — each adds a request that the browser has to fetch before the page feels ready. A store loading five custom font weights plus a live chat widget plus three tracking pixels is paying a speed tax for each. The fix is discipline: limit custom fonts to what's actually used, and audit whether every third-party widget earns its slowdown.
Speed problems are almost always additive — no single thing, but ten small things stacked up. The fix is subtraction.
A worked example
A store feels sluggish on mobile. You run PageSpeed Insights and get a mobile score in the 30s with warnings about JavaScript and image sizes. You scan the apps and find eighteen installed. You check the theme and it's an older premium theme heavily customised over three years. The diagnosis writes itself: app bloat plus oversized images plus a heavy theme. The fix plan: audit and cut apps to the essential few, compress and resize all images, and seriously consider migrating to a leaner modern theme. Each step claws back load time.
Why this matters beyond feel
Speed isn't vanity. Faster stores convert better because fewer shoppers give up waiting, and they rank better because Google rewards good page experience. If you're studying a fast competitor, their speed is part of why they win — and now you know how to check whether it's their lean theme, their disciplined app usage, or their optimised images doing the work. If you're fixing your own store, work through the four culprits above in order, re-testing after each, and watch the score climb.
Keep reading: practical fixes to speed up a slow theme, or how to find every app a store uses.