Quick answer
A slow Shopify store is usually caused by a mix of theme weight, too many apps, heavy images, third-party scripts, excessive sections, animations, and old custom code. Start with Shopify web performance reports, then audit what actually loads on the storefront.
Start with evidence
Do not guess. Shopify web performance reports show how the store performs across loading speed, interactivity, and visual stability. These are tied to Core Web Vitals, which measure how visitors experience the page.
After checking Shopify’s report, use browser developer tools or a performance tool to see what scripts, images, fonts, apps, and requests are loading on the page. The goal is not to chase a perfect score. The goal is to remove the things that slow down real shoppers without adding enough value.
Common causes
- Too many apps: especially apps that inject storefront scripts on every page.
- Old theme code: outdated architecture, unused snippets, heavy JavaScript, or abandoned customizations.
- Oversized images: large images used in places where smaller images would work.
- Too many homepage sections: especially sliders, videos, animations, maps, reviews, popups, and feeds all on one page.
- Third-party tags: ad pixels, chat widgets, heatmaps, reviews, subscriptions, loyalty, and tracking scripts.
- Animations and page transitions: often pretty, often expensive.
The app audit
Make a list of every app installed. For each app, answer:
- Does it load something on the storefront?
- Is it used on every page or only specific pages?
- Does it directly generate revenue, reduce support, or improve operations?
- Can the same job be done with theme settings, Shopify Flow, native features, or a lighter integration?
- If uninstalled, does it leave code behind?
One painful truth: uninstalling an app does not always remove every piece of theme code or embedded script. Shopify’s performance guidance also notes that you may need to contact the app developer for complete removal instructions.
What to fix first
- Remove unused apps and leftover scripts.
- Compress and resize images based on how they are displayed.
- Reduce homepage sections that do not help conversion.
- Turn off unnecessary animations.
- Move to an up-to-date theme if the current theme is the bottleneck.
- Test before and after each change so you know what actually helped.
Common misunderstanding
A speed score is not the whole user experience. A store can have a decent score and still feel heavy if popups, layout shifts, and slow scripts interrupt shopping.
How to test this
- Check Shopify web performance reports.
- Test the homepage, collection page, product page, cart, and blog separately.
- Measure before and after removing apps or scripts.
- Check mobile on a real device, not only desktop Lighthouse.
- Use a duplicate theme before removing old code.