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Shopify6 min read

Why is My Shopify Store Slow? (And How to Fix It)

Diagnosing a slow Shopify store is easier when you know where to look. Here are the most common causes of poor Shopify PageSpeed scores and how to address each one.

Why Shopify stores slow down over time

Shopify manages hosting and CDN for you, so the platform itself is rarely the bottleneck. The slowdown almost always comes from what gets added to a store after launch: apps, theme sections, tracking scripts, and marketing pixels.

Here are the most common causes and what you can do about each.

1. Too many Shopify apps

Every Shopify app you install has permission to inject JavaScript and CSS into your storefront. Many apps load their scripts on every page, not just the pages where they are actually used.

A review app running on checkout, a loyalty widget loading on collection pages, and a live chat widget firing on every product page can collectively add 500kb–2MB of JavaScript to your store.

What to do:

  • Audit your installed apps. If you are not actively using it, uninstall it — uninstalled apps often leave scripts behind.
  • Use your browser's Network tab to see which scripts load on product pages.
  • Ask app developers if their code can be loaded conditionally (e.g. only on pages where the feature appears).

    • 2. A heavy or poorly coded theme

    Online Store 2.0 themes give merchants enormous flexibility but that flexibility comes with a cost. Theme sections built with inline CSS, large bundled JS files, and unoptimized default images all contribute to slow scores.

    What to do:

  • Check your theme's PageSpeed score on a page with no apps installed (duplicate your theme temporarily).
  • If the theme scores well without apps, apps are your problem. If it scores poorly without apps, the theme itself needs work.
  • Avoid themes marketed purely on design. Look for themes that publish their own Lighthouse scores.

    • 3. Unoptimized product and hero images

    Shopify serves images via its CDN but it does not automatically reformat or compress images you upload. A 4MB JPEG uploaded as a product image stays a 4MB JPEG unless you handle it.

    What to do:

  • Use Shopify's built-in URL parameters to serve the correct size: append `_800x.webp` to image URLs in your theme's Liquid templates.
  • Upload images at 2x the display size maximum — a 600px wide product tile needs a 1200px image, not a 4000px original.
  • Use a bulk image compression app to process your existing library.

    • 4. Tracking pixels and marketing tags

    Facebook Pixel, Google Ads, TikTok Pixel, and Pinterest tags are each a separate script request. They add up fast, particularly on product and checkout pages where most fire simultaneously.

    What to do:

  • Load tracking scripts through Google Tag Manager and fire them on interaction rather than on page load.
  • Evaluate which pixels are actually converting — remove or pause the ones that are not producing data you act on.
  • Use Shopify's Customer Events API for server-side tracking where possible — it removes client-side script weight entirely.

    • 5. Video backgrounds and autoplay content

    Full-width video backgrounds on hero sections are one of the fastest ways to tank a Shopify mobile score. Autoplay video must download a significant portion before playback begins.

    What to do:

  • Replace video backgrounds with a static image on mobile using CSS media queries.
  • Use a poster image and lazy-load the video so it only loads when the user scrolls to it.
  • Host video on a CDN rather than Shopify's file storage.

    • How to diagnose your specific problem

    Run a free speed check with Loadzen on your most important pages — home, a collection, and a product page. The results will show your PageSpeed score, LCP, INP, and CLS with a prioritized list of fixes for your specific stack.

    Check your own site

    Run a free speed check with Loadzen and get a prioritized fix plan for your specific platform.

    Run free speed check