Why Shopify Stores Become Slow

Shopify is fast by default; what slows a store is almost always the combination of theme customizations, app injected scripts, and large unoptimized media. Every app can add liquid, JavaScript, and network calls to the critical rendering path, and merchants rarely remove apps they no longer use.

Image and video weight is the other major factor. Collection and product pages with huge galleries and autoplay content destroy LCP on mobile. Without explicit width/height, lazy loading discipline, and CDN-friendly formats, the theme cannot compensate.

Third-party marketing, reviews, and personalization widgets often load early and synchronously. Each vendor promises lift, but the stack as a whole caps conversion by slowing the first interaction. You need a tag strategy: what loads on all pages, what loads only on product, and what waits for interaction.

Theme upgrades and legacy code often leave dead sections, duplicate sections, and unused CSS. That debt increases maintenance time and makes every new A/B test riskier. Periodic theme audits and app rationalization are part of performance, not an optional cleanup.

Treat speed as a conversion input: measure p75 mobile LCP on your top product templates, not only the homepage. When those templates improve, you will feel it in add-to-cart and checkout completion, not only in PageSpeed scores.