Google measures how a page is served as well as what it says, so speed and layout stability came first. In May 2023, early in the project, the store failed the Core Web Vitals assessment on phones and on desktop. Its mobile performance score was 12 out of 100, and on desktop the layout moved so much while loading (a layout shift score of 0.69) that about four in five page loads rated poor.
Our developers went through the Stencil theme line by line:
- Removed unused JavaScript and render-blocking resources
- Lazy loaded JavaScript components to cut execution time
- Served images through Cloudflare's media optimization, sized for each device
- Built a custom image component with correct accessibility tags and lazy loading
- Rebuilt the carousel so it looks the same before and after JavaScript starts
- Trimmed the web fonts down to what the store uses
- Replaced the menu with a React navigation component that keeps the page's DOM small
- Gave each third-party app its own loading strategy: Stamped.io reviews, live chat, Searchanise search, back-in-stock notifications, and Google Tag Manager
By late 2023 the store passed Core Web Vitals for real Chrome users on desktop and scored 97 for performance, with 100 for accessibility, best practices, and SEO. A follow-up test in October 2024 showed the gains had held: all three vitals in the good range on phones and desktop, and a mobile layout shift of zero.
The full reports: before, May 2023 (mobile, desktop), and after, October 2024 (mobile, desktop). The methods are written up in our speed optimization guide, and the same work is available as BigCommerce speed optimization.