Add width and height or an aspect ratio for product, collection, and hero images. The browser can reserve the space before the image arrives.
Duplicate the live theme. Change one thing, use the same page and device, and record what happened. If the change breaks a customer path, roll it back before touching production.
Check the home, collection, product, cart, and checkout path on a phone. Confirm the page still works with a slow connection and that the business owner for the feature agrees it can change.
Add width and height or an aspect ratio for product, collection, and hero images. The browser can reserve the space before the image arrives.
Source: Shopify theme performance guidance. Reviewed Sep 22, 2026.