BigCommerce speed optimization, verified 100/100/100/100

Yes — and BigCommerce actually starts from a stronger position than most platforms here. It runs on Akamai's CDN with a median TTFB around 480ms, and ships built-in WebP conversion and responsive image srcsets with no app required. Our live before/after example shows a Stencil-themed product page rebuilt to a verified 100/100/100/100 mobile score, with both versions re-testable on live PageSpeed Insights.

Almost never the hosting — it's usually stacked apps and theme configuration. Each installed app injects its own script on every page regardless of whether that page uses it; stores running eight or more apps are common. The Stencil theme engine's Handlebars rendering adds overhead on top of that, and checkout pages often carry payment, fraud-detection, and upsell scripts that add another 0.3-0.8 seconds to checkout LCP.

A surprisingly common Stencil misconfiguration: setting the main hero or product image — the one that IS the Largest Contentful Paint element — to lazy-load. Lazy-loading is meant for below-the-fold images; applied to the LCP image itself, it does the opposite of what it's supposed to and delays the very metric it's meant to protect.

Often, yes. Third-party review apps typically inject their star rating markup after the page has already rendered, which pushes product card content down the moment the widget loads — a textbook Cumulative Layout Shift cause. Reserving a fixed height for that element before the widget populates it prevents the shift entirely.

It's real, and it's a genuine platform advantage. Since 2024, BigCommerce has shipped automatic WebP conversion, responsive srcsets, and on-the-fly resizing through Akamai Image Manager — baked into the platform with no app required, unlike most competitors where this needs a third-party plugin. It won't save an oversized 4000px source upload from being heavy on mobile, but it removes an entire category of manual work other platforms still require.

Typically 220KB to 350KB on the Cornerstone default theme — more than Shopify's roughly 180KB baseline, but less than Magento's 350KB-500KB. Stencil's Handlebars-based templates generate reasonably clean HTML on their own; most of that JavaScript weight comes from cart, wishlist, and faceted-search scripts layered on top, which is where theme-level tuning has the most room to work.