Shopify Speed Optimisation: How to Get a 90+ Google PageSpeed Score

Why Shopify Store Speed Directly Impacts Sales

Google research shows that a 1-second delay in mobile page load time reduces conversions by 20%. For a store doing £50k/month, that’s £10k in lost revenue from a single second of delay. Speed is not a technical luxury — it’s a revenue driver.

Google also uses Core Web Vitals as a ranking factor. Slow stores rank lower, attracting less organic traffic. The stores that win on SEO and conversion are those that have invested in performance optimisation.

Step 1: Audit Your Current Speed

Baseline your store before optimising. Use:

• Google PageSpeed Insights — free, gives CrUX field data (real user performance) and Lighthouse lab scores. Run on homepage, a collection page, and a product page.
• GTmetrix — detailed waterfall chart showing exactly which resources are slow
• WebPageTest — test from real mobile devices in real locations

Note your current LCP (Largest Contentful Paint), INP (Interaction to Next Paint), and CLS (Cumulative Layout Shift). These are the Core Web Vitals that affect both rankings and conversions.

Step 2: Image Optimisation (Biggest Impact)

Images account for 60–70% of total page weight on most Shopify stores. Three things to fix:

• Format — convert all images to WebP. Shopify’s CDN serves WebP automatically to supported browsers if you upload in WebP or enable the Shopify image transformation feature.
• Compression — product images under 200KB, hero/banner images under 400KB. Use Squoosh, TinyPNG, or the ShortPixel Shopify app for bulk compression.
• Dimensions — upload images at the maximum display size, not larger. A hero image displayed at 1400px wide doesn’t need to be uploaded at 4000px.
• Lazy loading — images below the fold should load only when scrolled into view. Modern Shopify themes do this natively; verify in PageSpeed Insights under “Defer offscreen images”.

Step 3: App Audit (Most Overlooked)

Every Shopify app that adds frontend functionality injects JavaScript and CSS into your storefront. A store with 20 apps may have 15 of them loading scripts on every page — even pages where those apps serve no purpose. Common offenders: reviews apps, loyalty apps, chat widgets, upsell popups, currency converters.

Audit process: install the Google Tag Manager overview or check PageSpeed Insights “Reduce JavaScript execution time” suggestions. List every script loading. Remove any app you haven’t actively used in 30 days. For apps you keep, check if they offer an “async” or “defer” loading option in their settings.

Step 4: Theme Optimisation

• Limit fonts — each Google Font adds an extra HTTP request. Use 1–2 font families maximum, pre-load them with <link rel=”preload”>
• Remove unused theme sections — many themes load JavaScript for features you’ve never enabled
• Minify CSS and JS — Shopify minifies assets in production by default, but check if your theme’s build process is configured correctly
• Enable browser caching — Shopify’s CDN handles this, but verify cache headers on your custom assets

Step 5: Fix Cumulative Layout Shift (CLS)

CLS measures how much the page layout shifts while loading — it’s what causes the frustrating “I was about to tap that button and the page jumped” experience on mobile. Common causes in Shopify: images without explicit width/height attributes, fonts loading after placeholder text, dynamic content like announcement bars injecting above content.

Fix: add width and height attributes to all <img> tags in your theme, preload your main font files, and ensure announcement bars have a reserved height in CSS.

Realistic Speed Goals

• Mobile PageSpeed score: 60–75 is good, 75–90 is great, 90+ is exceptional for Shopify
• LCP: under 2.5 seconds
• CLS: under 0.1
• Time to First Byte: under 800ms (Shopify’s CDN usually handles this well)

Need professional Shopify speed optimisation? Our development team delivers measurable performance improvements. Get a free speed audit or see our results.