Optimising Your Shopify Store for Speed
Jamie Chen
Lead Developer
Practical tips to improve your Shopify store's loading time and Core Web Vitals scores — and why page speed directly impacts your conversion rate and SEO rankings.
Every 100ms improvement in page load time can increase conversions by up to 1%. For a store turning over £1M a year, that's an extra £10k — and that's before you factor in the SEO uplift from better Core Web Vitals scores. Speed is not a nice-to-have. It's a revenue lever.
Understanding Core Web Vitals
Google's Core Web Vitals are three metrics that measure the real-world user experience of your store. They directly influence your search rankings — a slow store will rank lower than a fast competitor, all else being equal.
- LCP (Largest Contentful Paint): How quickly your main content loads. Aim for under 2.5 seconds.
- FID / INP (Interaction to Next Paint): How quickly your page responds to interaction. Aim for under 200ms.
- CLS (Cumulative Layout Shift): How stable your layout is as it loads. Aim for a score under 0.1.
The Biggest Culprits on Shopify Stores
In our experience auditing hundreds of Shopify stores, the same issues come up repeatedly. Here's what to fix first:
- 1Too many apps — every app adds JavaScript to your storefront. Audit your app list ruthlessly.
- 2Unoptimised images — use WebP format, compress to under 100KB for product images, and always set explicit width/height attributes.
- 3Render-blocking JavaScript — third-party scripts (chat widgets, review apps, tracking pixels) that load synchronously in the <head>.
- 4Large, unoptimised theme files — bloated CSS and JavaScript from themes that weren't built for performance.
- 5No lazy loading — images below the fold loading on page open instead of when needed.
Quick Wins You Can Do Today
- Compress and convert all product images to WebP using Shopify's built-in image transformation API
- Add loading="lazy" to all images that aren't above the fold
- Remove unused apps from your Shopify admin (even deactivated apps leave code behind until removed)
- Move non-critical scripts to load in the footer rather than the <head>
- Enable Shopify's built-in image CDN for global delivery
- Reduce the number of font variants you load (stick to 2 weights per typeface)
Advanced Optimisations
Once you've tackled the quick wins, these deeper changes will push your scores into the green:
- Replace heavy app functionality with lightweight native Shopify features where possible
- Implement section-level CSS loading so styles only load when the section is on the page
- Use Shopify's web pixel API instead of script tags for third-party tracking
- Implement critical CSS inlining for above-the-fold styles
- Audit and consolidate your third-party tag manager setup
“We consistently see stores achieve 20-40 point improvements in their Google PageSpeed scores within two weeks of a focused performance audit. The ROI is almost always immediate.”
Jamie Chen
Lead Developer, Flex Commerce
