Page speed is critical for eCommerce. Studies show that a 1-second delay in page load time can reduce conversions by 7%. On Shopify, a slow store doesn't just lose customers — it also ranks lower in Google. Speed is a confirmed ranking factor.
The good news? Most Shopify speed problems have simple fixes. In this guide, we'll show you how to diagnose your store's speed issues and fix them — from image compression to app audits to theme optimization.
Measure your store's speed (baseline first)
Before you fix anything, measure where you stand. Use these free tools:
- Google PageSpeed Insights — Go to pagespeedinsights.web.dev, enter your store's URL, and run the test for mobile. Pay attention to the Core Web Vitals section: Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS). Google aims for LCP under 2.5 seconds.
- GTmetrix — Provides more detailed performance metrics and a waterfall view of which resources load slowest.
- WebPageTest — Excellent for diagnosing specific bottlenecks and testing real devices/connections.
- RankCart's free audit — Run a free RankCart audit and check the Performance section. It gives you mobile and desktop LCP, plus a prioritised fix list.
Common causes of slow Shopify stores (and how to fix them)
1. Oversized product images
This is the #1 cause of slow Shopify stores. Most store owners upload images straight from their camera or product photography shoot — often 3–5 MB per image. When your homepage loads 10 product images, that's 30–50 MB of data for a single page.
Fix: Compress your images before uploading
- Use a tool like
ImageOptim(Mac),FileOptimizer(Windows), or online tools likeTinyPNG.comorSquoosh.app - Convert to WebP format where possible (more efficient than JPG/PNG)
- Aim for under 150–200 KB per product image without visible quality loss
- For Shopify: You can also use Shopify's built-in image optimization, or apps like "Image Optimizer" that auto-compress on upload
2. Too many apps
Every Shopify app adds code to your store — scripts, stylesheets, and API calls. Five or six apps are usually fine. Fifteen or twenty? You've got a problem. Each one slows your page load and increases the risk of conflicts.
Fix: Audit your apps and delete the ones you don't need
- Go to Shopify Admin → Apps and integrations
- List every app you have. Be honest: do you use all of them?
- Check which apps have the most negative reviews mentioning "slow" or "performance"
- Delete apps you don't actively use. Uninstalling removes their code from your store.
- If you need a feature, look for lightweight alternatives with fewer negative performance reviews
3. Render-blocking JavaScript and CSS
Some scripts and stylesheets block the browser from rendering your page until they fully load. This is necessary for some critical resources, but optional for others (analytics, chatbots, tracking pixels). Deferring non-critical resources speeds up page rendering.
Fix: Defer non-critical JavaScript
This is a bit technical, but your theme developer can help. In your theme code (theme.liquid or assets), look for scripts being loaded in the <head> tag. Move non-critical ones (analytics, tracking, chatbots) to the bottom of the <body> tag or add async or defer attributes.
4. Heavy or outdated theme
Some Shopify themes load lots of unnecessary code and design elements. If your theme was designed before 2024, it's likely not optimized for Core Web Vitals.
Fix: Switch to a lightweight theme or optimize your current one
- Lightweight themes recommended for speed: Dawn (Shopify's own), Impulse, Prestige, Taste
- If you love your current theme, contact the developer and ask about performance optimization. Many offer speed tuning services.
- Remove unused theme sections and features you don't need
5. Unoptimized code in your theme customizations
If you've added custom sections, apps, or embed code to your theme, it may not be optimized. Old code or memory leaks can slow your site.
Fix: Have your theme developer audit and clean up
- Work with your Shopify theme developer to review any custom code
- Remove unused CSS and JavaScript
- Implement lazy loading for images below the fold
Step-by-step speed optimization checklist
- Compress all images — Batch compress your entire product image library to under 200 KB each (target: 100–150 KB)
- Uninstall unused apps — Delete every app you're not actively using
- Delete unused theme sections — In your theme editor, remove sections and blocks you're not displaying
- Enable lazy loading for images — Shopify themes include this by default in newer versions. Check Settings → Performance.
- Check for render-blocking resources — Run PageSpeed Insights, scroll to "Opportunities", and look for "Eliminate render-blocking resources". Ask your developer to defer non-critical scripts.
- Minimize redirects — Each redirect adds 100–300ms. Check that your domain doesn't redirect multiple times before reaching your store.
- Enable Shopify CDN caching — Most Shopify plans include this. It's usually on by default, but confirm in Settings → Performance.
Want an automatic speed audit of your entire store? Run a free RankCart audit — it measures LCP, FID, and CLS on every page and gives you a prioritised fix list.
After you've optimized, test again
Speed optimization is iterative. After making changes:
- Wait 2–3 days for the changes to fully take effect
- Re-run your tests in PageSpeed Insights and GTmetrix
- Compare your new scores to your baseline
- Expect LCP to improve by 0.5–2 seconds with these fixes
Monitor speed over time
Speed degradation is common as your store grows. Set a reminder to test every 3 months.
- Each new app you install may slow your site
- New products and images add page weight
- Theme updates can sometimes impact performance
- Traffic spikes or Shopify infrastructure changes may affect speed
