Website Speed

Understanding Website Speed

Website speed is not a single number — it is a collection of metrics that together describe the loading experience. TTFB measures server response time. LCP measures when the largest visible element (usually the hero image or product photo) finishes rendering. FID (being replaced by Interaction to Next Paint, INP) measures how quickly the page responds to user input. CLS measures visual stability — whether elements shift around as the page loads.

The impact of speed on e-commerce revenue is well-documented. Studies consistently show that every 100ms of additional load time reduces conversion rates by approximately 1%. A product page that loads in 2 seconds will convert measurably better than the same page loading in 4 seconds. Google also uses Core Web Vitals as a ranking signal, meaning slow pages rank lower in search results and receive less organic traffic.

For Shopify stores, the most common speed killers are unoptimized images, too many third-party apps injecting JavaScript, render-blocking fonts, and heavy review and UGC widgets that load synchronously. Each app added to a Shopify store potentially adds JavaScript that runs on every page load. Stores with 15-20 apps commonly see page load times exceeding 5 seconds on mobile.

Speed optimization is an ongoing process, not a one-time fix. Common optimizations include lazy loading below-fold images, compressing and properly sizing images, minimizing third-party scripts, using a CDN for static assets, implementing browser caching, and deferring non-critical JavaScript. The highest-impact optimizations target the LCP element and reduce main-thread JavaScript execution time.