How We Achieved a 90+ PageSpeed Score on a Shopify Store

A PageSpeed score of 31 is not unusual for a Shopify store that's been live for a few years. Apps accumulate, images go un-optimised, and third-party scripts pile up. For this outdoor clothing brand, the slow site was costing them in both conversion rate and organic rankings — Google had started to demote them in mobile search results. The brief was clear: get above 90 without losing a single feature.

The Performance Audit

We started with a full Core Web Vitals audit. The Largest Contentful Paint (LCP) was 8.2 seconds — catastrophic. The main culprits were a 3.4MB hero image, seven third-party scripts loading synchronously in the head, and a review app injecting 140KB of CSS that blocked rendering. Total page weight was 9.1MB.

What We Fixed

1. 1Re-encoded all images to WebP format and implemented responsive image srcsets — saved 2.8MB from the hero alone.
2. 2Audited all 14 installed apps and removed 6 that had no measurable revenue impact.
3. 3Moved all third-party scripts to load asynchronously after the page paint.
4. 4Replaced the review app with a leaner alternative with 60% less JavaScript payload.
5. 5Implemented native lazy loading on all below-the-fold images.
6. 6Built a custom section for the hero using Liquid to avoid the app dependency entirely.
7. 7Removed 40KB of unused CSS from the base theme using PurgeCSS.
8. 8Preloaded the LCP image using a resource hint in the theme head.

The App Audit

Every app installed on Shopify adds JavaScript and CSS to the storefront whether it's actively used or not. We found three apps that hadn't been used in over a year but were still loading on every page. Removing unused apps is always the highest-leverage action on a performance project — and it's free.

Results

• PageSpeed mobile score improved from 31 to 92.
• Largest Contentful Paint improved from 8.2 seconds to 1.4 seconds.
• Total page weight reduced from 9.1MB to 2.3MB.
• Organic search impressions increased 34% in the 60 days following the improvement.
• Mobile conversion rate improved from 0.8% to 1.5% within 30 days.

Maintaining Performance

We documented a performance budget for the client — maximum JavaScript payload, image size guidelines, and a monthly app audit process. Performance improvements decay over time unless there's a process to protect them. We set up a Lighthouse CI check on their staging environment so any new app installation that degrades performance is flagged before it goes live.