Shopify handles hosting and content delivery well, so when a Shopify store is slow, the cause is usually on the storefront: apps, images, fonts and scripts added over time. The fixes are mostly a matter of removing things.
Measure with real-user data
Lab tests are useful for debugging, but what matters is how fast the store feels to real visitors on their own phones. Google's Core Web Vitals measure that:
| Metric | Measures | Good |
|---|---|---|
| Largest Contentful Paint (LCP) | When the main content appears | 2.5 s or less |
| Interaction to Next Paint (INP) | How quickly the page responds to taps | 200 ms or less |
| Cumulative Layout Shift (CLS) | How much the layout jumps around | 0.1 or less |
Check them in Google Search Console's Core Web Vitals report and in Shopify's own web performance reports in the admin. Look at mobile first.
1. Audit your apps
Every app that adds features to your storefront can add scripts. Some leave code behind after you uninstall them.
- List every installed app and ask whether you still need it.
- Uninstall the ones you don't.
- Check the theme code (or ask the app developer) for leftover snippets from removed apps.
- Where one app can replace three, consolidate.
2. Optimize images
- Upload images at sensible dimensions; a 5,000-pixel photo for a 600-pixel slot wastes bandwidth.
- Shopify's CDN serves resized, modern-format images when themes request them correctly. Modern themes do this; older or heavily customized ones may not.
- Make sure images below the fold are lazy-loaded, but the main product or hero image isn't.
- Give images set dimensions so the layout doesn't jump as they load.
3. Limit fonts
Each font family and weight is another download. Two families with two or three weights each is plenty. System fonts cost nothing to load.
4. Cut third-party scripts
Chat widgets, review carousels, pop-ups, tracking pixels and social feeds all add weight. Keep the ones that clearly earn their place, load the rest only where needed (a review widget only on product pages, say), and delay non-essential scripts until after the page is usable.
5. Simplify heavy theme features
Autoplay video backgrounds, multiple slideshows and animated sections look nice in the theme demo and cost a lot on a mid-range phone. A single strong image often converts as well and loads much faster.
6. Keep the theme current
Recent Shopify themes are built with performance in mind. A heavily modified theme from several years ago may be missing improvements. If you're planning a redesign, a modern, lean theme is often the biggest single speed gain.
Should you A/B test speed?
Speed improvements are generally safe to ship without testing. If you're removing a feature that might also affect sales (a pop-up, a review widget), an A/B test tells you whether the speed gain outweighs what the feature contributed. Testing tools themselves add scripts, so keep them lean and remove experiment code when tests end. For more on testing with mostly mobile traffic, see A/B testing for mobile.
Common questions
What slows down a Shopify store the most?
Usually third-party apps and scripts, oversized images, too many fonts and heavy theme features like video backgrounds and multiple sliders. The platform's own servers and CDN are rarely the bottleneck.
What are good Core Web Vitals scores?
Google's thresholds for a good experience are Largest Contentful Paint within 2.5 seconds, Interaction to Next Paint of 200 milliseconds or less, and Cumulative Layout Shift of 0.1 or less, measured at the 75th percentile of real visits.
Do A/B testing tools slow down Shopify?
Client-side testing tools add JavaScript and can cause flicker while the variant loads. Keep the testing script lean, test variants on real phones, and remove experiment code once a test ends.