How do I keep my app from slowing down merchant storefronts?
Merchants uninstall apps that slow their store. Speed is also part of Built for Shopify.
- Merchants say our app slows their store.
- How do we measure impact?
- What should we change?
Use theme app extensions instead of injecting code into themes, keep scripts small, load them only where needed and lazy-load anything below the fold. Measure storefront impact with Lighthouse and real-user web vitals before and after installing your app on test stores. Monitor after each release. Clean up fully on uninstall.
Common fixes
- Theme app extensions and app blocks.
- Smaller, deferred scripts.
- Load only on pages that need it.
- Optimized images and fonts.
- Clean uninstall.
How we look at it at ShoutEx
Our developers audit storefront impact and fix the heavy parts. Speed is part of Built for Shopify.
- Script tags on every page.
- Leftover code after uninstall.
- No performance tests.
- Large libraries loaded upfront.
- Theme app extensions.
- Small, deferred scripts.
- Before and after tests.
- Clean uninstall.
What developers and Shopify say
Here is what Shopify, developers and merchants say.
Community summaries describe recurring themes in public threads, not individual posts. Vendor pages describe vendor claims, so test them on your own calls.
Read next
Go deeper in the ShoutEx guides, or check the sources behind this answer.
We'll audit and fix performance.
Book a call →Follow-up questions
Do merchants check app speed?
Many run speed tests and blame apps.
What about headless stores?
Offer an API or SDK option.
How do we prove we're fast?
Publish test results in your docs.