Every additional second of load time costs conversions, and mobile shoppers on mid-tier phones feel your store very differently than you do on a desktop over office wifi. The good news: Shopify handles servers, CDN, and caching for you. The bad news: almost everything merchants add on top works against it.
Apps are the usual suspect
The average established store runs dozens of apps, and many inject JavaScript into every page whether needed or not. Audit quarterly: uninstall what you no longer use, and check whether removed apps left orphaned code in the theme, because many do. When evaluating replacements, prefer apps that render server-side or load only on the pages that use them.
Images do the rest of the damage
- Upload appropriately sized images instead of 5000-pixel originals; Shopify's CDN resizes, but source size still matters.
- Use the native image_tag filters so srcset, lazy loading, and width and height attributes come free.
- Keep the homepage hero light; it is usually the largest contentful paint element and therefore your LCP score.
Theme-level wins
Replace slider carousels with a single strong hero, since sliders load multiple large images to show one. Defer non-critical scripts, trim unused theme features, and consider whether that animated everything actually sells more products. If your theme predates Online Store 2.0, upgrading to a modern theme is often the single biggest speed jump available.
Measure like a customer
Test product and collection pages, not just the homepage, on a throttled mobile connection. Watch Core Web Vitals in Search Console for the field data Google actually uses. Set a performance budget before adding the next app, because speed is lost one small decision at a time.