Checkout.liquid customization not showing on theme preview

Topic summary

Checkout.liquid customizations are not appearing in the theme preview for a Shopify Plus store; the requester wants to avoid testing on the live theme.

Shopify Plus supports checkout.liquid, but the preview is not reflecting edits. The goal is to verify behavior in a preview environment only.

A responder asks whether checkout is actually activated on the shop (beyond merely having the checkout.liquid file present). This suggests the shop’s checkout settings may affect whether changes render.

Recommendation: Consider building with Checkout UI Extensions (Shopify’s API-based approach to customizing checkout) and refer to the provided developer docs link.

Technical notes:

  • checkout.liquid: a legacy Shopify Plus template for customizing the checkout page.
  • Checkout UI Extensions: modern, app-based extensions for checkout UI that are more robust and future-facing.

Status: No resolution yet. Action items include confirming checkout activation on the shop and evaluating a shift to Checkout UI Extensions. Unanswered question: whether preview environments can reliably show checkout.liquid changes.

Summarized with AI on January 31. AI used: gpt-5.

Customizations on checkout.liquid file don’t show up on the preview of a theme I’m editing.
I’m working on a store on the Shopify Plus plan, so checkout.liquid customizations should work.
I don’t want to test on the live/prod theme; that’s why I’m only interested in it working on a theme preview.

Are you sure that checkout is activated on that shop (and I don’t mean just having the file created).
If you are building with that file it’s going to make sense to start looking at extensions instead.

https://shopify.dev/docs/api/checkout-ui-extensions