Shopify's infrastructure is fast. Most slow Shopify stores are slow because of what has been added on top: apps, tracking tags, oversized images, and theme features nobody uses. The good news is that you can fix most of it without touching your theme's design.
Audit your apps first
Every app can inject its own JavaScript and CSS on every page, even pages where it does nothing. Uninstalled apps sometimes leave code behind in theme files too.
- List every installed app and remove the ones you no longer use.
- Search your theme code for leftover snippets from removed apps.
- For apps you keep, check whether they can be limited to the pages that need them.
Get product images under control
Product photography is usually the heaviest part of a store. Shopify's image CDN can resize and convert images on the fly, but only if your theme requests sensible sizes.
- Upload images no larger than about 2048 pixels on the longest side.
- Use the image_url filter with a width so phones do not download desktop-sized images.
- Lazy-load images below the fold, but never the main product image.
{{ product.featured_image | image_url: width: 900 | image_tag: loading: 'eager', fetchpriority: 'high' }}Defer third-party scripts
Reviews widgets, chat bubbles, and marketing pixels rarely need to load before the shopper can see the product. Loading them after the page is interactive is one of the biggest INP improvements you can make.
Or install one script
LightLoader applies image prioritization, script deferral, and layout reservation across your whole store from a single tag. Paste it into theme.liquid just before the closing head tag.
<script src="https://app.lightloader.com/api/loader.js?token=YOUR_TOKEN" async></script>Measure on a real product page