Shopify Speed Optimization Masterclass

Before optimizing anything, you need to understand what's broken. Most store owners guess—usually wrong—and waste effort on changes that don't matter. Run Google PageSpeed Insights on three pages: your homepage, your most popular collection page, and your best-selling product page. These have different performance profiles and different problems. Your homepage might be fast while your product pages are crawling because of review app bloat. Your collection pages might be slow because you're loading 48 products at once instead of 12. Shopify also provides a Speed Score under Online Store > Themes. This is less granular than PageSpeed but tracks changes over time—useful for catching regressions after app installs or theme updates. Pay attention to the specific recommendations these tools provide. They'll tell you exactly which resources are slow, which scripts are blocking rendering, which images are oversized. Most optimization is just working down this list systematically.

In the average Shopify store, images account for 50-70% of total page weight. This is where the biggest wins are hiding. I regularly see product photos uploaded at 4000px or higher—images that could print on a billboard—displayed in a 400px container. The browser still downloads the full file. It still processes all those pixels. Your customer's phone still struggles under the weight. The fix is simple: never upload images larger than 2048px for anything. For most product images, 1200-1500px provides more than enough detail for customers to zoom without creating performance problems. Use Shopify's built-in responsive images by including width parameters in your image URLs—the platform will serve appropriately sized versions to different devices. Lazy loading is the other half of the equation. Images below the fold shouldn't load until customers scroll toward them. Modern Shopify themes include this by default, but many older themes don't. If your theme loads all images on page load regardless of viewport position, you're paying a performance tax on every page view.

The average Shopify store has 6 apps installed. Many stores I audit have 15 or more. Here's what most merchants don't understand: every app potentially injects JavaScript on every page load, whether or not that page uses the app's features. A review app might load its entire script library on your homepage, even though reviews only display on product pages. A countdown timer app might inject code on every page even though you only use it during sales. A currency converter might load resources for all 50 currencies it supports even though you only sell in two countries. Go through every installed app and ask three questions: Is this providing measurable ROI? Could native Shopify functionality replace it? Is there a consolidated solution that replaces multiple single-purpose apps? Don't forget to check for zombie code. When you uninstall a Shopify app, it often leaves behind code in your theme that continues loading on every page. This is one of the most common hidden performance problems I find in audits.

Your theme is the foundation of your store's performance. Some themes are simply faster than others, and no amount of optimization will make a slow theme fast. Before buying a theme, check its performance on the demo store. If the demo is slow, your store will be slower. Look for themes built with performance in mind—they'll mention Lighthouse scores or Core Web Vitals in their marketing. If you're already committed to a theme, audit what you're actually using. Many themes come with dozens of features, sections, and scripts that you'll never touch. Each unused feature still adds weight. Work with a developer to remove what you don't need.