Checkout UI extensions not rendering on slow connections

Hey everyone,

We’ve noticed that on very slow connections, Checkout UI extensions sometimes load last — and in rare cases, don’t render fully.

This isn’t specific to our app (which loads instantly once initialized). We’ve seen the same behavior across other developers’ extensions too. During testing, we can see the skeleton UI appear where the extension should load, but it never completes — meanwhile, the shopper can still enter their details and complete checkout before any extensions finish rendering.

That becomes a real issue when the extension provides essential order information. In our case, merchants rely on this data for post-purchase operations, and missing it creates manual work to fix affected orders.

Questions:

  • Is Shopify aware of this load-order or rendering behavior?

  • Has anyone found a reliable workaround to ensure all extensions render before checkout completes?

We’ve considered using a checkout validation as a safeguard, but that could block checkout on extremely slow connections if extensions never finish loading. Even if this only affects a small percentage of users, at scale it impacts a significant number of orders.

Would really appreciate any insights or experiences from others who’ve encountered this.

Thanks!

Hey Alex!

If you’re working with extensions that provide essential order information, a checkout validation function is probably the best option here. It would ensure buyers won’t checkout providing the needed information.

The problem is that Shopify needs to load 2.54 MB of javascript to load checkout extensions:

No idea why they need that much code.